Fix a race condition in preference metric reporting.

chrome/browser/prefs/chrome_pref_service_factory.cc

Index: chrome/browser/prefs/chrome_pref_service_factory.cc
diff --git a/chrome/browser/prefs/chrome_pref_service_factory.cc b/chrome/browser/prefs/chrome_pref_service_factory.cc
index 67e8d6fe19489ef3f5b8fa305baf3fc24039a977..f20eade436e68b93cee0490e254cc490041f3a9e 100644
--- a/chrome/browser/prefs/chrome_pref_service_factory.cc
+++ b/chrome/browser/prefs/chrome_pref_service_factory.cc
@@ -17,6 +17,8 @@
 #include "base/prefs/pref_value_store.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/prefs/command_line_pref_store.h"
+#include "chrome/browser/prefs/pref_hash_filter.h"
+#include "chrome/browser/prefs/pref_hash_store.h"
 #include "chrome/browser/prefs/pref_model_associator.h"
 #include "chrome/browser/prefs/pref_service_syncable_builder.h"
 #include "chrome/browser/ui/profile_error_dialog.h"
@@ -77,6 +79,7 @@ void PrepareBuilder(
     base::SequencedTaskRunner* pref_io_task_runner,
     policy::PolicyService* policy_service,
     ManagedUserSettingsService* managed_user_settings,
+    scoped_ptr<PrefHashStore> pref_hash_store,
     const scoped_refptr<PrefStore>& extension_prefs,
     bool async) {
 #if defined(OS_LINUX)
@@ -116,7 +119,12 @@ void PrepareBuilder(
   builder->WithCommandLinePrefs(
       new CommandLinePrefStore(CommandLine::ForCurrentProcess()));
   builder->WithReadErrorCallback(base::Bind(&HandleReadError));
-  builder->WithUserPrefs(new JsonPrefStore(pref_filename, pref_io_task_runner));
+
+  builder->WithUserPrefs(
+      new JsonPrefStore(
+          pref_filename,
+          pref_io_task_runner,
+          scoped_ptr<PrefFilter>(new PrefHashFilter(pref_hash_store.Pass()))));
 }
 
 }  // namespace
@@ -135,6 +143,7 @@ PrefService* CreateLocalState(
                  pref_io_task_runner,
                  policy_service,
                  NULL,
+                 scoped_ptr<PrefHashStore>(),
                  NULL,
                  async);
   return builder.Create(pref_registry.get());
@@ -145,6 +154,7 @@ PrefServiceSyncable* CreateProfilePrefs(
     base::SequencedTaskRunner* pref_io_task_runner,
     policy::PolicyService* policy_service,
     ManagedUserSettingsService* managed_user_settings,
+    scoped_ptr<PrefHashStore> pref_hash_store,
     const scoped_refptr<PrefStore>& extension_prefs,
     const scoped_refptr<user_prefs::PrefRegistrySyncable>& pref_registry,
     bool async) {
@@ -155,6 +165,7 @@ PrefServiceSyncable* CreateProfilePrefs(
                  pref_io_task_runner,
                  policy_service,
                  managed_user_settings,
+                 pref_hash_store.Pass(),
                  extension_prefs,
                  async);
   return builder.CreateSyncable(pref_registry.get());