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..7c7f2ceb779050f46579cfea4479b69284f2c4dd 100644
--- a/base/prefs/json_pref_store.h
+++ b/base/prefs/json_pref_store.h
@@ -72,6 +72,15 @@ class BASE_PREFS_EXPORT JsonPrefStore
       const scoped_refptr<base::SequencedTaskRunner>& sequenced_task_runner,
       scoped_ptr<PrefFilter> pref_filter);
 
+  // Constructor for testing which allows an ImportantFileWriter to be
+  // specified.
+  JsonPrefStore(
+      const base::FilePath& pref_filename,
+      const base::FilePath& pref_alternate_filename,
+      const scoped_refptr<base::SequencedTaskRunner>& sequenced_task_runner,
+      scoped_ptr<base::ImportantFileWriter> file_writer,
+      scoped_ptr<PrefFilter> pref_filter);
+
   // PrefStore overrides:
   bool GetValue(const std::string& key,
                 const base::Value** result) const override;
@@ -190,6 +199,10 @@ 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_;
@@ -199,7 +212,7 @@ class BASE_PREFS_EXPORT JsonPrefStore
   bool read_only_;
 
   // Helper for safely writing pref data.
-  base::ImportantFileWriter writer_;
+  scoped_ptr<base::ImportantFileWriter> writer_;
 
   scoped_ptr<PrefFilter> pref_filter_;
   ObserverList<PrefStore::Observer, true> observers_;
@@ -208,6 +221,7 @@ 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_;