Pull GetMutableValue from Perisistent to WritablePrefStore.

base/prefs/writeable_pref_store.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_PREFS_WRITEABLE_PREF_STORE_H_
 #define BASE_PREFS_WRITEABLE_PREF_STORE_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/prefs/pref_store.h"
 
 namespace base {
 class Value;
 }
 
 // A pref store that can be written to as well as read from.
 class BASE_PREFS_EXPORT WriteablePrefStore : public PrefStore {
  public:
   WriteablePrefStore() {}
 
   // Sets a |value| for |key| in the store. Assumes ownership of |value|, which
   // must be non-NULL.
   virtual void SetValue(const std::string& key, base::Value* value) = 0;
 
   // Removes the value for |key|.
   virtual void RemoveValue(const std::string& key) = 0;
 
+  // Equivalent to PrefStore::GetValue but returns a mutable value.
+  virtual bool GetMutableValue(const std::string& key,
+                               base::Value** result) = 0;
+
+  // Triggers a value changed notification. This function needs to be called
+  // if one retrieves a list or dictionary with GetMutableValue and change its
+  // value. SetValue takes care of notifications itself. Note that
+  // ReportValueChanged will trigger notifications even if nothing has changed.
+  virtual void ReportValueChanged(const std::string& key) = 0;
+
+

[battre, 2014/06/13 09:16:00]

Nit: one blank line too much.

  protected:
   virtual ~WriteablePrefStore() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(WriteablePrefStore);
 };
 
 #endif  // BASE_PREFS_WRITEABLE_PREF_STORE_H_