Moved JsonPrefStore to use SequencedWorkerPool

chrome/browser/prefs/pref_service.cc

Index: chrome/browser/prefs/pref_service.cc
diff --git a/chrome/browser/prefs/pref_service.cc b/chrome/browser/prefs/pref_service.cc
index 10d7078989cfa4f7af59f96d16424134a12e45fb..61bb28df9301c2eab574fc66e33ae0e3b8990efd 100644
--- a/chrome/browser/prefs/pref_service.cc
+++ b/chrome/browser/prefs/pref_service.cc
@@ -16,6 +16,7 @@
 #include "base/stl_util.h"
 #include "base/string_number_conversions.h"
 #include "base/string_util.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "base/value_conversions.h"
 #include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
@@ -154,9 +155,9 @@ PrefService* PrefService::CreatePrefService(
 
   CommandLinePrefStore* command_line =
       new CommandLinePrefStore(CommandLine::ForCurrentProcess());
-  JsonPrefStore* user = new JsonPrefStore(
+  JsonPrefStore* user = JsonPrefStore::Create(
       pref_filename,
-      BrowserThread::GetMessageLoopProxyForThread(BrowserThread::FILE));
+      BrowserThread::GetBlockingPool());
   DefaultPrefStore* default_pref_store = new DefaultPrefStore();
 
   PrefNotifierImpl* pref_notifier = new PrefNotifierImpl();