Add reset all button to flags page

chrome/browser/about_flags.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 CHROME_BROWSER_ABOUT_FLAGS_H_
 #define CHROME_BROWSER_ABOUT_FLAGS_H_
 
 #include <map>
 #include <string>
 
@@ skipping 86 matching lines @@
 
 // Enables or disables the experiment with id |internal_name|.
 void SetExperimentEnabled(
     PrefService* prefs, const std::string& internal_name, bool enable);
 
 // Removes all switches that were added to a command line by a previous call to
 // |ConvertFlagsToSwitches()|.
 void RemoveFlagsSwitches(
     std::map<std::string, CommandLine::StringType>* switch_list);
 
+// Reset all flags to the default state by clearing all flags.
+void ResetAllFlags(PrefService* prefs);
+
 // Returns the value for the current platform. This is one of the values defined
 // by the OS enum above.
 // This is exposed only for testing.
 int GetCurrentPlatform();
 
 // Sends UMA stats about experimental flag usage. This should be called once per
 // startup.
 void RecordUMAStatistics(const PrefService* prefs);
 
 namespace testing {
 // Clears internal global state, for unit tests.
 void ClearState();
 
 // Sets the list of experiments. Pass in NULL to use the default set. This does
 // NOT take ownership of the supplied Experiments.
 void SetExperiments(const Experiment* e, size_t count);
 
 // Returns the current set of experiments.
 const Experiment* GetExperiments(size_t* count);
 
 // Separator used for multi values. Multi values are represented in prefs as
 // name-of-experiment + kMultiSeparator + selected_index.
 extern const char kMultiSeparator[];
 
 }  // namespace testing
 
 }  // namespace about_flags
 
 #endif  // CHROME_BROWSER_ABOUT_FLAGS_H_