Moved JsonPrefStore to use SequencedWorkerPool

chrome/common/json_pref_store.cc

Index: chrome/common/json_pref_store.cc
diff --git a/chrome/common/json_pref_store.cc b/chrome/common/json_pref_store.cc
index ed30346ff048190d9ad004b210f14be3ffca8cf7..71fbccba8aa1e927ff30cf7ab73134748b6fff6e 100644
--- a/chrome/common/json_pref_store.cc
+++ b/chrome/common/json_pref_store.cc
@@ -1,4 +1,3 @@
-// Copyright (c) 2012 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.
 
@@ -13,6 +12,8 @@
 #include "base/json/json_string_value_serializer.h"
 #include "base/memory/ref_counted.h"
 #include "base/message_loop_proxy.h"
+#include "base/sequenced_task_runner.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "base/values.h"
 
 namespace {
@@ -26,25 +27,25 @@ class FileThreadDeserializer
     : public base::RefCountedThreadSafe<FileThreadDeserializer> {
  public:
   FileThreadDeserializer(JsonPrefStore* delegate,
-                         base::MessageLoopProxy* file_loop_proxy)
+                         base::SequencedTaskRunner* sequenced_task_runner)
       : no_dir_(false),
         error_(PersistentPrefStore::PREF_READ_ERROR_NONE),
         delegate_(delegate),
-        file_loop_proxy_(file_loop_proxy),
+        sequenced_task_runner_(sequenced_task_runner),
         origin_loop_proxy_(base::MessageLoopProxy::current()) {
   }
 
   void Start(const FilePath& path) {
     DCHECK(origin_loop_proxy_->BelongsToCurrentThread());
-    file_loop_proxy_->PostTask(
+    sequenced_task_runner_->PostTask(
         FROM_HERE,
         base::Bind(&FileThreadDeserializer::ReadFileAndReport,
                    this, path));
   }
 
-  // Deserializes JSON on the file thread.
+  // Deserializes JSON on the sequenced task runner.
   void ReadFileAndReport(const FilePath& path) {
-    DCHECK(file_loop_proxy_->BelongsToCurrentThread());
+    DCHECK(sequenced_task_runner_->RunsTasksOnCurrentThread());
 
     value_.reset(DoReading(path, &error_, &no_dir_));
 
@@ -85,7 +86,7 @@ class FileThreadDeserializer
   PersistentPrefStore::PrefReadError error_;
   scoped_ptr<Value> value_;
   scoped_refptr<JsonPrefStore> delegate_;
-  scoped_refptr<base::MessageLoopProxy> file_loop_proxy_;
+  scoped_refptr<base::SequencedTaskRunner> sequenced_task_runner_;
   scoped_refptr<base::MessageLoopProxy> origin_loop_proxy_;
 };
 
@@ -137,13 +138,25 @@ void FileThreadDeserializer::HandleErrors(
 
 }  // namespace
 
+JsonPrefStore* JsonPrefStore::Create(
+    const FilePath& filename, base::SequencedWorkerPool* worker_pool) {
+  // Make sure that write requests for the same set of files don't step on
+  // each other by using parent directory keyed (profile dir) sequenced task
+  // runner.
+  scoped_refptr<base::SequencedTaskRunner> task_runner =
+      worker_pool->GetSequencedTaskRunnerWithShutdownBehavior(
+          worker_pool->GetNamedSequenceToken(filename.DirName().AsUTF8Unsafe()),
+          base::SequencedWorkerPool::BLOCK_SHUTDOWN);
+  return new JsonPrefStore(filename, task_runner.get());
+}
+
 JsonPrefStore::JsonPrefStore(const FilePath& filename,
-                             base::MessageLoopProxy* file_message_loop_proxy)
+                             base::SequencedTaskRunner* sequenced_task_runner)
     : path_(filename),
-      file_message_loop_proxy_(file_message_loop_proxy),
+      sequenced_task_runner_(sequenced_task_runner),
       prefs_(new DictionaryValue()),
       read_only_(false),
-      writer_(filename, file_message_loop_proxy),
+      writer_(filename, sequenced_task_runner),
       error_delegate_(NULL),
       initialized_(false),
       read_error_(PREF_READ_ERROR_OTHER) {
@@ -245,7 +258,7 @@ void JsonPrefStore::ReadPrefsAsync(ReadErrorDelegate *error_delegate) {
   // Start async reading of the preferences file. It will delete itself
   // in the end.
   scoped_refptr<FileThreadDeserializer> deserializer(
-      new FileThreadDeserializer(this, file_message_loop_proxy_.get()));
+      new FileThreadDeserializer(this, sequenced_task_runner_.get()));
   deserializer->Start(path_);
 }