Move preference MACs to the protected preference stores.

base/prefs/value_map_pref_store.h

Index: base/prefs/value_map_pref_store.h
diff --git a/base/prefs/value_map_pref_store.h b/base/prefs/value_map_pref_store.h
index 29d0b382edfb0b6e71463072bf713ea0039bc588..c202725d947bdd8cab1eb46d88f62fa75fabd9d3 100644
--- a/base/prefs/value_map_pref_store.h
+++ b/base/prefs/value_map_pref_store.h
@@ -30,6 +30,9 @@ class BASE_PREFS_EXPORT ValueMapPrefStore : public WriteablePrefStore {
   // WriteablePrefStore overrides:
   virtual void SetValue(const std::string& key, base::Value* value) OVERRIDE;
   virtual void RemoveValue(const std::string& key) OVERRIDE;
+  virtual bool GetMutableValue(const std::string& key,
+                               base::Value** value) OVERRIDE;
+  virtual void ReportValueChanged(const std::string& key) OVERRIDE;
 
  protected:
   virtual ~ValueMapPrefStore();