Revert 274735 "Use FSEvents for recursive file watch on Mac"

Broke Mac tests:

http://build.chromium.org/p/chromium.mac/buildstatus?builder=Mac10.6%20Tests%20%281%29&number=52768
http://build.chromium.org/p/chromium.mac/buildstatus?builder=Mac10.6%20Tests%20%282%29&number=52019
http://build.chromium.org/p/chromium.mac/buildstatus?builder=Mac%2010.6%20Tests%20%28dbg%29%283%29&number=50243
http://build.chromium.org/p/chromium.mac/buildstatus?builder=Mac%2010.6%20Tests%20%28dbg%29%284%29&number=41693


> Use FSEvents for recursive file watch on Mac
> 
> Brings back the old FSEvents code, changing it to support recursive watches only, and use dispatch queues instead of using the CFRunLoop from the UI thread.
> 
> BUG=144491
> 
> Review URL: https://codereview.chromium.org/283423003

TBR=vandebo@chromium.org

Review URL: https://codereview.chromium.org/316853003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@274757 0039d316-1c4b-4281-b951-d872f2087c98


CrOS-Libchrome-Original-Commit: 1595e8383f59e8c348d97c918df3ffdacaa8d987
diff --git a/base/files/file_path_watcher.h b/base/files/file_path_watcher.h
index 229254c..3c1941f 100644
--- a/base/files/file_path_watcher.h
+++ b/base/files/file_path_watcher.h
@@ -93,7 +93,7 @@
   // true, to watch |path| and its children. The callback will be invoked on
   // the same loop. Returns true on success.
   //
-  // Recursive watch is not supported on all platforms and file systems.
+  // NOTE: Recursive watch is not supported on all platforms and file systems.
   // Watch() will return false in the case of failure.
   bool Watch(const FilePath& path, bool recursive, const Callback& callback);
 
diff --git a/base/files/file_path_watcher_browsertest.cc b/base/files/file_path_watcher_browsertest.cc
index 4ec8aba..2bdcf13 100644
--- a/base/files/file_path_watcher_browsertest.cc
+++ b/base/files/file_path_watcher_browsertest.cc
@@ -205,8 +205,9 @@
   bool result;
   file_thread_.message_loop_proxy()->PostTask(
       FROM_HERE,
-      base::Bind(SetupWatchCallback, target, watcher, delegate, recursive_watch,
-                 &result, &completion));
+      base::Bind(SetupWatchCallback,
+                 target, watcher, delegate, recursive_watch, &result,
+                 &completion));
   completion.Wait();
   return result;
 }
@@ -482,7 +483,7 @@
   DeleteDelegateOnFileThread(subdir_delegate.release());
 }
 
-#if defined(OS_WIN) || defined(OS_LINUX) || defined(OS_MACOSX)
+#if defined(OS_WIN) || defined(OS_LINUX)
 TEST_F(FilePathWatcherTest, RecursiveWatch) {
   FilePathWatcher watcher;
   FilePath dir(temp_dir_.path().AppendASCII("dir"));
@@ -547,45 +548,6 @@
 }
 #endif
 
-#if defined(OS_LINUX) || defined(OS_MACOSX)
-TEST_F(FilePathWatcherTest, RecursiveWithSymLink) {
-  FilePathWatcher watcher;
-  FilePath test_dir(temp_dir_.path().AppendASCII("test_dir"));
-  ASSERT_TRUE(base::CreateDirectory(test_dir));
-  FilePath symlink(test_dir.AppendASCII("symlink"));
-  scoped_ptr<TestDelegate> delegate(new TestDelegate(collector()));
-  ASSERT_TRUE(SetupWatch(symlink, &watcher, delegate.get(), true));
-
-  // Link creation.
-  FilePath target1(temp_dir_.path().AppendASCII("target1"));
-  ASSERT_TRUE(base::CreateSymbolicLink(target1, symlink));
-  ASSERT_TRUE(WaitForEvents());
-
-  // Target1 creation.
-  ASSERT_TRUE(base::CreateDirectory(target1));
-  ASSERT_TRUE(WaitForEvents());
-
-  // Create a file in target1.
-  FilePath target1_file(target1.AppendASCII("file"));
-  ASSERT_TRUE(WriteFile(target1_file, "content"));
-  ASSERT_TRUE(WaitForEvents());
-
-  // Link change.
-  FilePath target2(temp_dir_.path().AppendASCII("target2"));
-  ASSERT_TRUE(base::CreateDirectory(target2));
-  ASSERT_TRUE(base::DeleteFile(symlink, false));
-  ASSERT_TRUE(base::CreateSymbolicLink(target2, symlink));
-  ASSERT_TRUE(WaitForEvents());
-
-  // Create a file in target2.
-  FilePath target2_file(target2.AppendASCII("file"));
-  ASSERT_TRUE(WriteFile(target2_file, "content"));
-  ASSERT_TRUE(WaitForEvents());
-
-  DeleteDelegateOnFileThread(delegate.release());
-}
-#endif
-
 TEST_F(FilePathWatcherTest, MoveChild) {
   FilePathWatcher file_watcher;
   FilePathWatcher subdir_watcher;
diff --git a/base/files/file_path_watcher_fsevents.cc b/base/files/file_path_watcher_fsevents.cc
deleted file mode 100644
index d7fa657..0000000
--- a/base/files/file_path_watcher_fsevents.cc
+++ /dev/null
@@ -1,263 +0,0 @@
-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "base/files/file_path_watcher_fsevents.h"
-
-#include <list>
-
-#include "base/bind.h"
-#include "base/file_util.h"
-#include "base/lazy_instance.h"
-#include "base/logging.h"
-#include "base/mac/libdispatch_task_runner.h"
-#include "base/mac/scoped_cftyperef.h"
-#include "base/message_loop/message_loop.h"
-
-namespace base {
-
-namespace {
-
-// The latency parameter passed to FSEventsStreamCreate().
-const CFAbsoluteTime kEventLatencySeconds = 0.3;
-
-class FSEventsTaskRunner : public mac::LibDispatchTaskRunner {
- public:
-   FSEventsTaskRunner()
-       : mac::LibDispatchTaskRunner("chromium.org.FilePathWatcherFSEvents") {
-   }
-
- protected:
-   virtual ~FSEventsTaskRunner() {}
-};
-
-static LazyInstance<FSEventsTaskRunner>::Leaky g_task_runner =
-    LAZY_INSTANCE_INITIALIZER;
-
-// Resolve any symlinks in the path.
-FilePath ResolvePath(const FilePath& path) {
-  const unsigned kMaxLinksToResolve = 255;
-
-  std::vector<FilePath::StringType> component_vector;
-  path.GetComponents(&component_vector);
-  std::list<FilePath::StringType>
-      components(component_vector.begin(), component_vector.end());
-
-  FilePath result;
-  unsigned resolve_count = 0;
-  while (resolve_count < kMaxLinksToResolve && !components.empty()) {
-    FilePath component(*components.begin());
-    components.pop_front();
-
-    FilePath current;
-    if (component.IsAbsolute()) {
-      current = component;
-    } else {
-      current = result.Append(component);
-    }
-
-    FilePath target;
-    if (ReadSymbolicLink(current, &target)) {
-      if (target.IsAbsolute())
-        result.clear();
-      std::vector<FilePath::StringType> target_components;
-      target.GetComponents(&target_components);
-      components.insert(components.begin(), target_components.begin(),
-                        target_components.end());
-      resolve_count++;
-    } else {
-      result = current;
-    }
-  }
-
-  if (resolve_count >= kMaxLinksToResolve)
-    result.clear();
-  return result;
-}
-
-// The callback passed to FSEventStreamCreate().
-void FSEventsCallback(ConstFSEventStreamRef stream,
-                      void* event_watcher, size_t num_events,
-                      void* event_paths, const FSEventStreamEventFlags flags[],
-                      const FSEventStreamEventId event_ids[]) {
-  FilePathWatcherFSEvents* watcher =
-      reinterpret_cast<FilePathWatcherFSEvents*>(event_watcher);
-  DCHECK(g_task_runner.Get().RunsTasksOnCurrentThread());
-
-  bool root_changed = watcher->ResolveTargetPath();
-  std::vector<FilePath> paths;
-  FSEventStreamEventId root_change_at = FSEventStreamGetLatestEventId(stream);
-  for (size_t i = 0; i < num_events; i++) {
-    if (flags[i] & kFSEventStreamEventFlagRootChanged)
-      root_changed = true;
-    if (event_ids[i])
-      root_change_at = std::min(root_change_at, event_ids[i]);
-    paths.push_back(FilePath(
-        reinterpret_cast<char**>(event_paths)[i]).StripTrailingSeparators());
-  }
-
-  // Reinitialize the event stream if we find changes to the root. This is
-  // necessary since FSEvents doesn't report any events for the subtree after
-  // the directory to be watched gets created.
-  if (root_changed) {
-    // Resetting the event stream from within the callback fails (FSEvents spews
-    // bad file descriptor errors), so post a task to do the reset.
-    g_task_runner.Get().PostTask(
-        FROM_HERE,
-        Bind(&FilePathWatcherFSEvents::UpdateEventStream, watcher,
-             root_change_at));
-  }
-
-  watcher->OnFilePathsChanged(paths);
-}
-
-}  // namespace
-
-FilePathWatcherFSEvents::FilePathWatcherFSEvents() : fsevent_stream_(NULL) {
-}
-
-void FilePathWatcherFSEvents::OnFilePathsChanged(
-    const std::vector<FilePath>& paths) {
-  if (!message_loop()->BelongsToCurrentThread()) {
-    message_loop()->PostTask(
-        FROM_HERE,
-        Bind(&FilePathWatcherFSEvents::OnFilePathsChanged, this, paths));
-    return;
-  }
-
-  DCHECK(message_loop()->BelongsToCurrentThread());
-  if (resolved_target_.empty())
-    return;
-
-  for (size_t i = 0; i < paths.size(); i++) {
-    if (resolved_target_.IsParent(paths[i]) || resolved_target_ == paths[i]) {
-      callback_.Run(target_, false);
-      return;
-    }
-  }
-}
-
-bool FilePathWatcherFSEvents::Watch(const FilePath& path,
-                                    bool recursive,
-                                    const FilePathWatcher::Callback& callback) {
-  DCHECK(resolved_target_.empty());
-  DCHECK(MessageLoopForIO::current());
-  DCHECK(!callback.is_null());
-
-  // This class could support non-recursive watches, but that is currently
-  // left to FilePathWatcherKQueue.
-  if (!recursive)
-    return false;
-
-  set_message_loop(MessageLoopProxy::current());
-  callback_ = callback;
-  target_ = path;
-
-  FSEventStreamEventId start_event = FSEventsGetCurrentEventId();
-  g_task_runner.Get().PostTask(
-      FROM_HERE,
-      Bind(&FilePathWatcherFSEvents::StartEventStream, this, start_event));
-  return true;
-}
-
-void FilePathWatcherFSEvents::Cancel() {
-  if (callback_.is_null()) {
-    // Watch was never called, so exit.
-    set_cancelled();
-    return;
-  }
-
-  // Switch to the dispatch queue thread if necessary, so we can tear down
-  // the event stream.
-  if (!g_task_runner.Get().RunsTasksOnCurrentThread()) {
-    g_task_runner.Get().PostTask(
-        FROM_HERE,
-        Bind(&FilePathWatcherFSEvents::CancelOnMessageLoopThread, this));
-  } else {
-    CancelOnMessageLoopThread();
-  }
-}
-
-void FilePathWatcherFSEvents::CancelOnMessageLoopThread() {
-  // For all other implementations, the "message loop thread" is the IO thread,
-  // as returned by message_loop(). This implementation, however, needs to
-  // cancel pending work on the Dipatch Queue thread.
-  DCHECK(g_task_runner.Get().RunsTasksOnCurrentThread());
-
-  set_cancelled();
-  if (fsevent_stream_) {
-    DestroyEventStream();
-    callback_.Reset();
-    target_.clear();
-    resolved_target_.clear();
-  }
-}
-
-void FilePathWatcherFSEvents::UpdateEventStream(
-    FSEventStreamEventId start_event) {
-  DCHECK(g_task_runner.Get().RunsTasksOnCurrentThread());
-
-  // It can happen that the watcher gets canceled while tasks that call this
-  // function are still in flight, so abort if this situation is detected.
-  if (is_cancelled() || resolved_target_.empty())
-    return;
-
-  if (fsevent_stream_)
-    DestroyEventStream();
-
-  ScopedCFTypeRef<CFStringRef> cf_path(CFStringCreateWithCString(
-      NULL, resolved_target_.value().c_str(), kCFStringEncodingMacHFS));
-  ScopedCFTypeRef<CFStringRef> cf_dir_path(CFStringCreateWithCString(
-      NULL, resolved_target_.DirName().value().c_str(),
-      kCFStringEncodingMacHFS));
-  CFStringRef paths_array[] = { cf_path.get(), cf_dir_path.get() };
-  ScopedCFTypeRef<CFArrayRef> watched_paths(CFArrayCreate(
-      NULL, reinterpret_cast<const void**>(paths_array), arraysize(paths_array),
-      &kCFTypeArrayCallBacks));
-
-  FSEventStreamContext context;
-  context.version = 0;
-  context.info = this;
-  context.retain = NULL;
-  context.release = NULL;
-  context.copyDescription = NULL;
-
-  fsevent_stream_ = FSEventStreamCreate(NULL, &FSEventsCallback, &context,
-                                        watched_paths,
-                                        start_event,
-                                        kEventLatencySeconds,
-                                        kFSEventStreamCreateFlagWatchRoot);
-  FSEventStreamSetDispatchQueue(fsevent_stream_,
-                                g_task_runner.Get().GetDispatchQueue());
-
-  if (!FSEventStreamStart(fsevent_stream_))
-    message_loop()->PostTask(FROM_HERE, Bind(callback_, target_, true));
-}
-
-bool FilePathWatcherFSEvents::ResolveTargetPath() {
-  DCHECK(g_task_runner.Get().RunsTasksOnCurrentThread());
-  FilePath resolved = ResolvePath(target_).StripTrailingSeparators();
-  bool changed = resolved != resolved_target_;
-  resolved_target_ = resolved;
-  if (resolved_target_.empty())
-    message_loop()->PostTask(FROM_HERE, Bind(callback_, target_, true));
-  return changed;
-}
-
-void FilePathWatcherFSEvents::DestroyEventStream() {
-  FSEventStreamStop(fsevent_stream_);
-  FSEventStreamInvalidate(fsevent_stream_);
-  FSEventStreamRelease(fsevent_stream_);
-  fsevent_stream_ = NULL;
-}
-
-void FilePathWatcherFSEvents::StartEventStream(
-    FSEventStreamEventId start_event) {
-  DCHECK(g_task_runner.Get().RunsTasksOnCurrentThread());
-  ResolveTargetPath();
-  UpdateEventStream(start_event);
-}
-
-FilePathWatcherFSEvents::~FilePathWatcherFSEvents() {}
-
-}  // namespace base
diff --git a/base/files/file_path_watcher_fsevents.h b/base/files/file_path_watcher_fsevents.h
deleted file mode 100644
index 5640b4d..0000000
--- a/base/files/file_path_watcher_fsevents.h
+++ /dev/null
@@ -1,73 +0,0 @@
-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef BASE_FILES_FILE_PATH_WATCHER_FSEVENTS_H_
-#define BASE_FILES_FILE_PATH_WATCHER_FSEVENTS_H_
-
-#include <CoreServices/CoreServices.h>
-
-#include <vector>
-
-#include "base/files/file_path.h"
-#include "base/files/file_path_watcher.h"
-
-namespace base {
-
-// Mac-specific file watcher implementation based on FSEvents.
-// There are trade-offs between the FSEvents implementation and a kqueue
-// implementation. The biggest issues are that FSEvents on 10.6 sometimes drops
-// events and kqueue does not trigger for modifications to a file in a watched
-// directory. See file_path_watcher_mac.cc for the code that decides when to
-// use which one.
-class FilePathWatcherFSEvents : public FilePathWatcher::PlatformDelegate {
- public:
-  FilePathWatcherFSEvents();
-
-  // Called from the FSEvents callback whenever there is a change to the paths.
-  void OnFilePathsChanged(const std::vector<FilePath>& paths);
-
-  // (Re-)Initialize the event stream to start reporting events from
-  // |start_event|.
-  void UpdateEventStream(FSEventStreamEventId start_event);
-
-  // Returns true if resolving the target path got a different result than
-  // last time it was done.
-  bool ResolveTargetPath();
-
-  // FilePathWatcher::PlatformDelegate overrides.
-  virtual bool Watch(const FilePath& path,
-                     bool recursive,
-                     const FilePathWatcher::Callback& callback) OVERRIDE;
-  virtual void Cancel() OVERRIDE;
-
- private:
-  virtual ~FilePathWatcherFSEvents();
-
-  // Destroy the event stream.
-  void DestroyEventStream();
-
-  // Start watching the FSEventStream.
-  void StartEventStream(FSEventStreamEventId start_event);
-
-  // Cleans up and stops the event stream.
-  virtual void CancelOnMessageLoopThread() OVERRIDE;
-
-  // Callback to notify upon changes.
-  FilePathWatcher::Callback callback_;
-
-  // Target path to watch (passed to callback).
-  FilePath target_;
-
-  // Target path with all symbolic links resolved.
-  FilePath resolved_target_;
-
-  // Backend stream we receive event callbacks from (strong reference).
-  FSEventStreamRef fsevent_stream_;
-
-  DISALLOW_COPY_AND_ASSIGN(FilePathWatcherFSEvents);
-};
-
-}  // namespace base
-
-#endif  // BASE_FILES_FILE_PATH_WATCHER_FSEVENTS_H_
diff --git a/base/files/file_path_watcher_kqueue.cc b/base/files/file_path_watcher_kqueue.cc
index c38e344..e035f22 100644
--- a/base/files/file_path_watcher_kqueue.cc
+++ b/base/files/file_path_watcher_kqueue.cc
@@ -2,14 +2,19 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "base/files/file_path_watcher_kqueue.h"
+#include "base/files/file_path_watcher.h"
 
 #include <fcntl.h>
+#include <sys/event.h>
 #include <sys/param.h>
 
+#include <vector>
+
 #include "base/bind.h"
 #include "base/file_util.h"
 #include "base/logging.h"
+#include "base/message_loop/message_loop.h"
+#include "base/message_loop/message_loop_proxy.h"
 #include "base/strings/stringprintf.h"
 
 // On some platforms these are not defined.
@@ -22,18 +27,136 @@
 
 namespace base {
 
-FilePathWatcherKQueue::FilePathWatcherKQueue() : kqueue_(-1) {}
+namespace {
 
-FilePathWatcherKQueue::~FilePathWatcherKQueue() {}
+// Mac-specific file watcher implementation based on kqueue.
+// Originally it was based on FSEvents so that the semantics were equivalent
+// on Linux, OSX and Windows where it was able to detect:
+// - file creation/deletion/modification in a watched directory
+// - file creation/deletion/modification for a watched file
+// - modifications to the paths to a watched object that would affect the
+//   object such as renaming/attibute changes etc.
+// The FSEvents version did all of the above except handling attribute changes
+// to path components. Unfortunately FSEvents appears to have an issue where the
+// current implementation (Mac OS X 10.6.7) sometimes drops events and doesn't
+// send notifications. See
+// http://code.google.com/p/chromium/issues/detail?id=54822#c31 for source that
+// will reproduce the problem. FSEvents also required having a CFRunLoop
+// backing the thread that it was running on, that caused added complexity
+// in the interfaces.
+// The kqueue implementation will handle all of the items in the list above
+// except for detecting modifications to files in a watched directory. It will
+// detect the creation and deletion of files, just not the modification of
+// files. It does however detect the attribute changes that the FSEvents impl
+// would miss.
+class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate,
+                            public MessageLoopForIO::Watcher,
+                            public MessageLoop::DestructionObserver {
+ public:
+  FilePathWatcherImpl() : kqueue_(-1) {}
 
-void FilePathWatcherKQueue::ReleaseEvent(struct kevent& event) {
+  // MessageLoopForIO::Watcher overrides.
+  virtual void OnFileCanReadWithoutBlocking(int fd) OVERRIDE;
+  virtual void OnFileCanWriteWithoutBlocking(int fd) OVERRIDE;
+
+  // MessageLoop::DestructionObserver overrides.
+  virtual void WillDestroyCurrentMessageLoop() OVERRIDE;
+
+  // FilePathWatcher::PlatformDelegate overrides.
+  virtual bool Watch(const FilePath& path,
+                     bool recursive,
+                     const FilePathWatcher::Callback& callback) OVERRIDE;
+  virtual void Cancel() OVERRIDE;
+
+ protected:
+  virtual ~FilePathWatcherImpl() {}
+
+ private:
+  class EventData {
+   public:
+    EventData(const FilePath& path, const FilePath::StringType& subdir)
+        : path_(path), subdir_(subdir) { }
+    FilePath path_;  // Full path to this item.
+    FilePath::StringType subdir_;  // Path to any sub item.
+  };
+  typedef std::vector<struct kevent> EventVector;
+
+  // Can only be called on |io_message_loop_|'s thread.
+  virtual void CancelOnMessageLoopThread() OVERRIDE;
+
+  // Returns true if the kevent values are error free.
+  bool AreKeventValuesValid(struct kevent* kevents, int count);
+
+  // Respond to a change of attributes of the path component represented by
+  // |event|. Sets |target_file_affected| to true if |target_| is affected.
+  // Sets |update_watches| to true if |events_| need to be updated.
+  void HandleAttributesChange(const EventVector::iterator& event,
+                              bool* target_file_affected,
+                              bool* update_watches);
+
+  // Respond to a move or deletion of the path component represented by
+  // |event|. Sets |target_file_affected| to true if |target_| is affected.
+  // Sets |update_watches| to true if |events_| need to be updated.
+  void HandleDeleteOrMoveChange(const EventVector::iterator& event,
+                                bool* target_file_affected,
+                                bool* update_watches);
+
+  // Respond to a creation of an item in the path component represented by
+  // |event|. Sets |target_file_affected| to true if |target_| is affected.
+  // Sets |update_watches| to true if |events_| need to be updated.
+  void HandleCreateItemChange(const EventVector::iterator& event,
+                              bool* target_file_affected,
+                              bool* update_watches);
+
+  // Update |events_| with the current status of the system.
+  // Sets |target_file_affected| to true if |target_| is affected.
+  // Returns false if an error occurs.
+  bool UpdateWatches(bool* target_file_affected);
+
+  // Fills |events| with one kevent per component in |path|.
+  // Returns the number of valid events created where a valid event is
+  // defined as one that has a ident (file descriptor) field != -1.
+  static int EventsForPath(FilePath path, EventVector *events);
+
+  // Release a kevent generated by EventsForPath.
+  static void ReleaseEvent(struct kevent& event);
+
+  // Returns a file descriptor that will not block the system from deleting
+  // the file it references.
+  static uintptr_t FileDescriptorForPath(const FilePath& path);
+
+  static const uintptr_t kNoFileDescriptor = static_cast<uintptr_t>(-1);
+
+  // Closes |*fd| and sets |*fd| to -1.
+  static void CloseFileDescriptor(uintptr_t* fd);
+
+  // Returns true if kevent has open file descriptor.
+  static bool IsKeventFileDescriptorOpen(const struct kevent& event) {
+    return event.ident != kNoFileDescriptor;
+  }
+
+  static EventData* EventDataForKevent(const struct kevent& event) {
+    return reinterpret_cast<EventData*>(event.udata);
+  }
+
+  EventVector events_;
+  scoped_refptr<base::MessageLoopProxy> io_message_loop_;
+  MessageLoopForIO::FileDescriptorWatcher kqueue_watcher_;
+  FilePathWatcher::Callback callback_;
+  FilePath target_;
+  int kqueue_;
+
+  DISALLOW_COPY_AND_ASSIGN(FilePathWatcherImpl);
+};
+
+void FilePathWatcherImpl::ReleaseEvent(struct kevent& event) {
   CloseFileDescriptor(&event.ident);
   EventData* entry = EventDataForKevent(event);
   delete entry;
   event.udata = NULL;
 }
 
-int FilePathWatcherKQueue::EventsForPath(FilePath path, EventVector* events) {
+int FilePathWatcherImpl::EventsForPath(FilePath path, EventVector* events) {
   DCHECK(MessageLoopForIO::current());
   // Make sure that we are working with a clean slate.
   DCHECK(events->empty());
@@ -75,14 +198,14 @@
   return last_existing_entry;
 }
 
-uintptr_t FilePathWatcherKQueue::FileDescriptorForPath(const FilePath& path) {
+uintptr_t FilePathWatcherImpl::FileDescriptorForPath(const FilePath& path) {
   int fd = HANDLE_EINTR(open(path.value().c_str(), O_EVTONLY));
   if (fd == -1)
     return kNoFileDescriptor;
   return fd;
 }
 
-void FilePathWatcherKQueue::CloseFileDescriptor(uintptr_t* fd) {
+void FilePathWatcherImpl::CloseFileDescriptor(uintptr_t* fd) {
   if (*fd == kNoFileDescriptor) {
     return;
   }
@@ -93,7 +216,7 @@
   *fd = kNoFileDescriptor;
 }
 
-bool FilePathWatcherKQueue::AreKeventValuesValid(struct kevent* kevents,
+bool FilePathWatcherImpl::AreKeventValuesValid(struct kevent* kevents,
                                                int count) {
   if (count < 0) {
     DPLOG(ERROR) << "kevent";
@@ -127,7 +250,7 @@
   return valid;
 }
 
-void FilePathWatcherKQueue::HandleAttributesChange(
+void FilePathWatcherImpl::HandleAttributesChange(
     const EventVector::iterator& event,
     bool* target_file_affected,
     bool* update_watches) {
@@ -151,7 +274,7 @@
   }
 }
 
-void FilePathWatcherKQueue::HandleDeleteOrMoveChange(
+void FilePathWatcherImpl::HandleDeleteOrMoveChange(
     const EventVector::iterator& event,
     bool* target_file_affected,
     bool* update_watches) {
@@ -167,7 +290,7 @@
   }
 }
 
-void FilePathWatcherKQueue::HandleCreateItemChange(
+void FilePathWatcherImpl::HandleCreateItemChange(
     const EventVector::iterator& event,
     bool* target_file_affected,
     bool* update_watches) {
@@ -187,7 +310,7 @@
   }
 }
 
-bool FilePathWatcherKQueue::UpdateWatches(bool* target_file_affected) {
+bool FilePathWatcherImpl::UpdateWatches(bool* target_file_affected) {
   // Iterate over events adding kevents for items that exist to the kqueue.
   // Then check to see if new components in the path have been created.
   // Repeat until no new components in the path are detected.
@@ -228,7 +351,7 @@
   return true;
 }
 
-void FilePathWatcherKQueue::OnFileCanReadWithoutBlocking(int fd) {
+void FilePathWatcherImpl::OnFileCanReadWithoutBlocking(int fd) {
   DCHECK(MessageLoopForIO::current());
   DCHECK_EQ(fd, kqueue_);
   DCHECK(events_.size());
@@ -301,24 +424,24 @@
   }
 }
 
-void FilePathWatcherKQueue::OnFileCanWriteWithoutBlocking(int fd) {
+void FilePathWatcherImpl::OnFileCanWriteWithoutBlocking(int fd) {
   NOTREACHED();
 }
 
-void FilePathWatcherKQueue::WillDestroyCurrentMessageLoop() {
+void FilePathWatcherImpl::WillDestroyCurrentMessageLoop() {
   CancelOnMessageLoopThread();
 }
 
-bool FilePathWatcherKQueue::Watch(const FilePath& path,
-                                  bool recursive,
-                                  const FilePathWatcher::Callback& callback) {
+bool FilePathWatcherImpl::Watch(const FilePath& path,
+                                bool recursive,
+                                const FilePathWatcher::Callback& callback) {
   DCHECK(MessageLoopForIO::current());
   DCHECK(target_.value().empty());  // Can only watch one path.
   DCHECK(!callback.is_null());
   DCHECK_EQ(kqueue_, -1);
 
   if (recursive) {
-    // Recursive watch is not supported using kqueue.
+    // Recursive watch is not supported on this platform.
     NOTIMPLEMENTED();
     return false;
   }
@@ -355,7 +478,7 @@
       kqueue_, true, MessageLoopForIO::WATCH_READ, &kqueue_watcher_, this);
 }
 
-void FilePathWatcherKQueue::Cancel() {
+void FilePathWatcherImpl::Cancel() {
   base::MessageLoopProxy* proxy = io_message_loop_.get();
   if (!proxy) {
     set_cancelled();
@@ -363,13 +486,13 @@
   }
   if (!proxy->BelongsToCurrentThread()) {
     proxy->PostTask(FROM_HERE,
-                    base::Bind(&FilePathWatcherKQueue::Cancel, this));
+                    base::Bind(&FilePathWatcherImpl::Cancel, this));
     return;
   }
   CancelOnMessageLoopThread();
 }
 
-void FilePathWatcherKQueue::CancelOnMessageLoopThread() {
+void FilePathWatcherImpl::CancelOnMessageLoopThread() {
   DCHECK(MessageLoopForIO::current());
   if (!is_cancelled()) {
     set_cancelled();
@@ -386,4 +509,10 @@
   }
 }
 
+}  // namespace
+
+FilePathWatcher::FilePathWatcher() {
+  impl_ = new FilePathWatcherImpl();
+}
+
 }  // namespace base
diff --git a/base/files/file_path_watcher_kqueue.h b/base/files/file_path_watcher_kqueue.h
deleted file mode 100644
index 703fda6..0000000
--- a/base/files/file_path_watcher_kqueue.h
+++ /dev/null
@@ -1,132 +0,0 @@
-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef BASE_FILES_FILE_PATH_WATCHER_KQUEUE_H_
-#define BASE_FILES_FILE_PATH_WATCHER_KQUEUE_H_
-
-#include <sys/event.h>
-#include <vector>
-
-#include "base/files/file_path.h"
-#include "base/files/file_path_watcher.h"
-#include "base/message_loop/message_loop.h"
-#include "base/message_loop/message_loop_proxy.h"
-
-namespace base {
-
-// Mac-specific file watcher implementation based on kqueue.
-// The Linux and Windows versions are able to detect:
-// - file creation/deletion/modification in a watched directory
-// - file creation/deletion/modification for a watched file
-// - modifications to the paths to a watched object that would affect the
-//   object such as renaming/attibute changes etc.
-// The kqueue implementation will handle all of the items in the list above
-// except for detecting modifications to files in a watched directory. It will
-// detect the creation and deletion of files, just not the modification of
-// files. It does however detect the attribute changes that the FSEvents impl
-// would miss.
-class FilePathWatcherKQueue : public FilePathWatcher::PlatformDelegate,
-                              public MessageLoopForIO::Watcher,
-                              public MessageLoop::DestructionObserver {
- public:
-  FilePathWatcherKQueue();
-
-  // MessageLoopForIO::Watcher overrides.
-  virtual void OnFileCanReadWithoutBlocking(int fd) OVERRIDE;
-  virtual void OnFileCanWriteWithoutBlocking(int fd) OVERRIDE;
-
-  // MessageLoop::DestructionObserver overrides.
-  virtual void WillDestroyCurrentMessageLoop() OVERRIDE;
-
-  // FilePathWatcher::PlatformDelegate overrides.
-  virtual bool Watch(const FilePath& path,
-                     bool recursive,
-                     const FilePathWatcher::Callback& callback) OVERRIDE;
-  virtual void Cancel() OVERRIDE;
-
- protected:
-  virtual ~FilePathWatcherKQueue();
-
- private:
-  class EventData {
-   public:
-    EventData(const FilePath& path, const FilePath::StringType& subdir)
-        : path_(path), subdir_(subdir) { }
-    FilePath path_;  // Full path to this item.
-    FilePath::StringType subdir_;  // Path to any sub item.
-  };
-
-  typedef std::vector<struct kevent> EventVector;
-
-  // Can only be called on |io_message_loop_|'s thread.
-  virtual void CancelOnMessageLoopThread() OVERRIDE;
-
-  // Returns true if the kevent values are error free.
-  bool AreKeventValuesValid(struct kevent* kevents, int count);
-
-  // Respond to a change of attributes of the path component represented by
-  // |event|. Sets |target_file_affected| to true if |target_| is affected.
-  // Sets |update_watches| to true if |events_| need to be updated.
-  void HandleAttributesChange(const EventVector::iterator& event,
-                              bool* target_file_affected,
-                              bool* update_watches);
-
-  // Respond to a move or deletion of the path component represented by
-  // |event|. Sets |target_file_affected| to true if |target_| is affected.
-  // Sets |update_watches| to true if |events_| need to be updated.
-  void HandleDeleteOrMoveChange(const EventVector::iterator& event,
-                                bool* target_file_affected,
-                                bool* update_watches);
-
-  // Respond to a creation of an item in the path component represented by
-  // |event|. Sets |target_file_affected| to true if |target_| is affected.
-  // Sets |update_watches| to true if |events_| need to be updated.
-  void HandleCreateItemChange(const EventVector::iterator& event,
-                              bool* target_file_affected,
-                              bool* update_watches);
-
-  // Update |events_| with the current status of the system.
-  // Sets |target_file_affected| to true if |target_| is affected.
-  // Returns false if an error occurs.
-  bool UpdateWatches(bool* target_file_affected);
-
-  // Fills |events| with one kevent per component in |path|.
-  // Returns the number of valid events created where a valid event is
-  // defined as one that has a ident (file descriptor) field != -1.
-  static int EventsForPath(FilePath path, EventVector *events);
-
-  // Release a kevent generated by EventsForPath.
-  static void ReleaseEvent(struct kevent& event);
-
-  // Returns a file descriptor that will not block the system from deleting
-  // the file it references.
-  static uintptr_t FileDescriptorForPath(const FilePath& path);
-
-  static const uintptr_t kNoFileDescriptor = static_cast<uintptr_t>(-1);
-
-  // Closes |*fd| and sets |*fd| to -1.
-  static void CloseFileDescriptor(uintptr_t* fd);
-
-  // Returns true if kevent has open file descriptor.
-  static bool IsKeventFileDescriptorOpen(const struct kevent& event) {
-    return event.ident != kNoFileDescriptor;
-  }
-
-  static EventData* EventDataForKevent(const struct kevent& event) {
-    return reinterpret_cast<EventData*>(event.udata);
-  }
-
-  EventVector events_;
-  scoped_refptr<base::MessageLoopProxy> io_message_loop_;
-  MessageLoopForIO::FileDescriptorWatcher kqueue_watcher_;
-  FilePathWatcher::Callback callback_;
-  FilePath target_;
-  int kqueue_;
-
-  DISALLOW_COPY_AND_ASSIGN(FilePathWatcherKQueue);
-};
-
-}  // namespace base
-
-#endif  // BASE_FILES_FILE_PATH_WATCHER_KQUEUE_H_
diff --git a/base/files/file_path_watcher_linux.cc b/base/files/file_path_watcher_linux.cc
index 915ad50..0bdca62 100644
--- a/base/files/file_path_watcher_linux.cc
+++ b/base/files/file_path_watcher_linux.cc
@@ -463,7 +463,6 @@
 }
 
 void FilePathWatcherImpl::CancelOnMessageLoopThread() {
-  DCHECK(message_loop()->BelongsToCurrentThread());
   set_cancelled();
 
   if (!callback_.is_null()) {