base: Remove most uses of MessageLoopProxy

Replace most usage of MessageLoopProxy under base/ with SingleThreadTaskRunner
and ThreadTaskRunnerHandle (excluding the implementation of MessageLoopProxy
itself which will removed later).

This patch was mostly autogenerated with
https://codereview.chromium.org/1010073002.

Depends on https://codereview.chromium.org/1086733002/.

BUG=465354
TBR=nkostylev@chromium.org,pkasting@chromium.org,pauljensen@chromium.org

Review URL: https://codereview.chromium.org/1100773004

Cr-Commit-Position: refs/heads/master@{#327755}


CrOS-Libchrome-Original-Commit: 054861d0934c663de3cea933e1d65fd8319856a6
diff --git a/base/files/file_proxy_unittest.cc b/base/files/file_proxy_unittest.cc
index dbf1476..df0bbc8 100644
--- a/base/files/file_proxy_unittest.cc
+++ b/base/files/file_proxy_unittest.cc
@@ -9,7 +9,6 @@
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/memory/weak_ptr.h"
-#include "base/message_loop/message_loop.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_restrictions.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -79,7 +78,7 @@
   }
 
   TaskRunner* file_task_runner() const {
-    return file_thread_.message_loop_proxy().get();
+    return file_thread_.task_runner().get();
   }
   const FilePath& test_dir_path() const { return dir_.path(); }
   const FilePath test_path() const { return dir_.path().AppendASCII("test"); }