Moved JsonPrefStore to use SequencedWorkerPool

base/prefs/json_pref_store.h

Index: base/prefs/json_pref_store.h
diff --git a/base/prefs/json_pref_store.h b/base/prefs/json_pref_store.h
index 3ed1ffb13301761809cfc5a707edc8c60c2c9ffa..e818f9baca2246daf10e2b0b8103b0373fb0bd89 100644
--- a/base/prefs/json_pref_store.h
+++ b/base/prefs/json_pref_store.h
@@ -18,7 +18,8 @@
 
 namespace base {
 class DictionaryValue;
-class MessageLoopProxy;
+class SequencedWorkerPool;
+class SequencedTaskRunner;
 class Value;
 }
 
@@ -28,10 +29,16 @@ 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.
+  // Returns instance of SequencedTaskRunner which guarantees that file
+  // operations on the same file will be executed in sequenced order.
+  static scoped_refptr<base::SequencedTaskRunner> GetTaskRunnerForFile(
+      const FilePath& pref_filename,
+      base::SequencedWorkerPool* worker_pool);
+
+  // |sequenced_task_runner| is must be a shutdown-blocking task runner, ideally
+  // created by GetTaskRunnerForFile() method above.
   JsonPrefStore(const FilePath& pref_filename,
-                base::MessageLoopProxy* file_message_loop_proxy);
+                base::SequencedTaskRunner* sequenced_task_runner);
 
   // PrefStore overrides:
   virtual ReadResult GetValue(const std::string& key,
@@ -69,7 +76,7 @@ class JsonPrefStore : public PersistentPrefStore,
   virtual bool SerializeData(std::string* output) OVERRIDE;
 
   FilePath path_;
-  scoped_refptr<base::MessageLoopProxy> file_message_loop_proxy_;
+  const scoped_refptr<base::SequencedTaskRunner> sequenced_task_runner_;
 
   scoped_ptr<base::DictionaryValue> prefs_;