POSIX: don't allocate memory after forking.

Previously we would allocate memory in the child process. However, the
allocation might have happened while the malloc lock was held,
resulting in a deadlock.

This patch removes allocation from the child but probably makes Mac's
startup time slower until a Mac person can implement
dir_reader_posix.h.

TEST=Unittest for new code
BUG=36678

http://codereview.chromium.org/672003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@41275 0039d316-1c4b-4281-b951-d872f2087c98


CrOS-Libchrome-Original-Commit: ef73044e42948214832dd11dd3326b738f816eb6
diff --git a/base/dir_reader_fallback.h b/base/dir_reader_fallback.h
new file mode 100644
index 0000000..c8f02e6
--- /dev/null
+++ b/base/dir_reader_fallback.h
@@ -0,0 +1,30 @@
+// Copyright (c) 2010 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_DIR_READER_FALLBACK_H_
+#define BASE_DIR_READER_FALLBACK_H_
+
+namespace base {
+
+class DirReaderFallback {
+ public:
+  // Open a directory. If |IsValid| is true, then |Next| can be called to start
+  // the iteration at the beginning of the directory.
+  explicit DirReaderFallback(const char* directory_path) { }
+  // After construction, IsValid returns true iff the directory was
+  // successfully opened.
+  bool IsValid() const { return false; }
+  // Move to the next entry returning false if the iteration is complete.
+  bool Next() { return false; }
+  // Return the name of the current directory entry.
+  const char* name() { return 0;}
+  // Return the file descriptor which is being used.
+  int fd() const { return -1; }
+  // Returns true if this is a no-op fallback class (for testing).
+  static bool IsFallback() { return true; }
+};
+
+}  // namespace base
+
+#endif  // BASE_DIR_READER_FALLBACK_H_