Implement lossy pref behavior for JsonPrefStore.

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 2ad546da613df9386fdc6735c80761b2d399e3bb..d418bc0294813a288e4631eb7a67b2c7b6358d4b 100644
--- a/base/prefs/json_pref_store.h
+++ b/base/prefs/json_pref_store.h
@@ -190,6 +190,10 @@ class BASE_PREFS_EXPORT JsonPrefStore
                         scoped_ptr<base::DictionaryValue> prefs,
                         bool schedule_write);
 
+  // Schedule a write with the file writer as long as |flags| doesn't contain
+  // WriteablePrefStore::LOSSY_PREF_WRITE_FLAG.
+  void ScheduleWrite(uint32 flags);
+
   const base::FilePath path_;
   const base::FilePath alternate_path_;
   const scoped_refptr<base::SequencedTaskRunner> sequenced_task_runner_;
@@ -208,6 +212,7 @@ class BASE_PREFS_EXPORT JsonPrefStore
 
   bool initialized_;
   bool filtering_in_progress_;
+  bool pending_lossy_write_;
   PrefReadError read_error_;
 
   std::set<std::string> keys_need_empty_value_;