[Mac] Use NSTitlebarAccessoryViewController to implement colored app window frames.

base/mac/sdk_forward_declarations.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.
 
 // This file contains forward declarations for items in later SDKs than the
 // default one with which Chromium is built (currently 10.6).
 // If you call any function from this header, be sure to check at runtime for
 // respondsToSelector: before calling these functions (else your code will crash
 // on older OS X versions that chrome still supports).
 
@@ skipping 390 matching lines @@
 @end
 
 BASE_EXPORT extern "C" NSString* const NSUserActivityTypeBrowsingWeb;
 
 BASE_EXPORT extern "C" NSString* const NSAppearanceNameVibrantDark;
 
 @interface CBUUID (YosemiteSDK)
 - (NSString*)UUIDString;
 @end
 
+@class NSTitlebarAccessoryViewController;
+@interface NSWindow (YosemiteSDK)
+- (void)addTitlebarAccessoryViewController:(NSTitlebarAccessoryViewController *)childViewController;
+- (void)removeTitlebarAccessoryViewControllerAtIndex:(NSInteger)index;
+@end
+
 #endif  // MAC_OS_X_VERSION_10_10
 
 #endif  // BASE_MAC_SDK_FORWARD_DECLARATIONS_H_