Change PrefStore::ReadResult to a boolean.

base/prefs/persistent_pref_store.h

 // Copyright (c) 2012 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_PERSISTENT_PREF_STORE_H_
 #define BASE_PREFS_PERSISTENT_PREF_STORE_H_
 
 #include <string>
 
 #include "base/prefs/base_prefs_export.h"
@@ skipping 23 matching lines @@
   };
 
   class ReadErrorDelegate {
    public:
     virtual ~ReadErrorDelegate() {}
 
     virtual void OnError(PrefReadError error) = 0;
   };
 
   // Equivalent to PrefStore::GetValue but returns a mutable value.
-  virtual ReadResult GetMutableValue(const std::string& key,
-                                     base::Value** result) = 0;
+  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;
 
   // 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;
@@ skipping 30 matching lines @@
   virtual void ReadPrefsAsync(ReadErrorDelegate* error_delegate) = 0;
 
   // Lands any pending writes to disk.
   virtual void CommitPendingWrite() = 0;
 
  protected:
   virtual ~PersistentPrefStore() {}
 };
 
 #endif  // BASE_PREFS_PERSISTENT_PREF_STORE_H_