Leftover cleanups from https://codereview.chromium.org/324493002 .

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"
@@ skipping 18 matching lines @@
   // 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;
 
+  // Same as SetValue, but doesn't generate notifications. This is used by
+  // PrefService::GetMutableUserPref() in order to put empty entries
+  // into the user pref store. Using SetValue is not an option since existing
+  // tests rely on the number of notifications generated.
+  virtual void SetValueSilently(const std::string& key, base::Value* value) = 0;
 
  protected:
   virtual ~WriteablePrefStore() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(WriteablePrefStore);
 };
 
 #endif  // BASE_PREFS_WRITEABLE_PREF_STORE_H_