Moved JsonPrefStore to use SequencedWorkerPool

chrome/common/json_pref_store.h

Index: chrome/common/json_pref_store.h
diff --git a/chrome/common/json_pref_store.h b/chrome/common/json_pref_store.h
index 7ceb7dad2ac0c472e51a1405e58861e6fd6ad93a..0b9fcbf891215a4c26e68e79303d960e03ad8457 100644
--- a/chrome/common/json_pref_store.h
+++ b/chrome/common/json_pref_store.h
@@ -18,7 +18,8 @@
 
 namespace base {
 class DictionaryValue;
-class MessageLoopProxy;
+class SequencedWorkerPool;
+class SequencedTaskRunner;
 class Value;
 }
 
@@ -28,10 +29,11 @@ class FilePath;
 class JsonPrefStore : public PersistentPrefStore,
                       public ImportantFileWriter::DataSerializer {
  public:
-  // |file_message_loop_proxy| is the MessageLoopProxy for a thread on which
-  // file I/O can be done.
-  JsonPrefStore(const FilePath& pref_filename,
-                base::MessageLoopProxy* file_message_loop_proxy);
+  // |worker_pool| is the SequencedWorkerPool on which file I/O can be done.
+  // The worker pool will also ensure that write requests for the same file are
+  // sequenced properly and that such requests block shutdown.
+  static JsonPrefStore* Create(const FilePath& pref_filename,
+                               base::SequencedWorkerPool* worker_pool);
 
   // PrefStore overrides:
   virtual ReadResult GetValue(const std::string& key,
@@ -63,13 +65,16 @@ class JsonPrefStore : public PersistentPrefStore,
   void OnFileRead(base::Value* value_owned, PrefReadError error, bool no_dir);
 
  private:
+  // |task_runner| is the TaskRunner for a thread on which file I/O can be done.
+  JsonPrefStore(const FilePath& pref_filename,
+                base::SequencedTaskRunner* sequenced_task_runner);
   virtual ~JsonPrefStore();
 
   // ImportantFileWriter::DataSerializer overrides:
   virtual bool SerializeData(std::string* output) OVERRIDE;
 
   FilePath path_;
-  scoped_refptr<base::MessageLoopProxy> file_message_loop_proxy_;
+  scoped_refptr<base::SequencedTaskRunner> sequenced_task_runner_;
 
   scoped_ptr<base::DictionaryValue> prefs_;