gn/linux: warnings as errors, turn on Wextra

ui/keyboard/keyboard_util.h

 // Copyright (c) 2013 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 UI_KEYBOARD_KEYBOARD_UTIL_H_
 #define UI_KEYBOARD_KEYBOARD_UTIL_H_
 
 #include <string>
 
 #include "base/strings/string16.h"
@@ skipping 110 matching lines @@
 KEYBOARD_EXPORT bool SendKeyEvent(std::string type,
                                    int key_value,
                                    int key_code,
                                    std::string key_name,
                                    int modifiers,
                                    aura::WindowTreeHost* host);
 
 // Marks that the keyboard load has started. This is used to measure the time it
 // takes to fully load the keyboard. This should be called before
 // MarkKeyboardLoadFinished.
-KEYBOARD_EXPORT const void MarkKeyboardLoadStarted();
+KEYBOARD_EXPORT void MarkKeyboardLoadStarted();
 
 // Marks that the keyboard load has ended. This finishes measuring that the
 // keyboard is loaded.
-KEYBOARD_EXPORT const void MarkKeyboardLoadFinished();
+KEYBOARD_EXPORT void MarkKeyboardLoadFinished();
 
 // Get the list of keyboard resources. |size| is populated with the number of
 // resources in the returned array.
 KEYBOARD_EXPORT const GritResourceMap* GetKeyboardExtensionResources(
     size_t* size);
 
 // Sets the override content url.
 // This is used by for input view for extension IMEs.
 KEYBOARD_EXPORT void SetOverrideContentUrl(const GURL& url);
 
 // Gets the override content url.
 KEYBOARD_EXPORT const GURL& GetOverrideContentUrl();
 
 // Logs the keyboard control event as a UMA stat.
 void LogKeyboardControlEvent(KeyboardControlEvent event);
 
 }  // namespace keyboard
 
 #endif  // UI_KEYBOARD_KEYBOARD_UTIL_H_