[Mac] Use NSThemeFrame instead of NSGrayFrame on 10.8.

chrome/browser/ui/cocoa/browser_frame_view.h

 // Copyright (c) 2011 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.
 
 #import <Cocoa/Cocoa.h>
 
 // BrowserFrameView is a class whose methods we swizzle into NSGrayFrame
-// (an AppKit framework class) so that we can support custom frame drawing.
+// on 10.7 and below, or NSThemeFrame on 10.8 and above, so that we can
+// support custom frame drawing. This is used with a textured window so that
+// AppKit does not draw a title bar.
 // This class is never to be instantiated on its own.
 // We explored a variety of ways to support custom frame drawing and custom
 // window widgets.
 // Our requirements were:
 // a) that we could fall back on standard system drawing at any time for the
 //    "default theme"
 // b) We needed to be able to draw both a background pattern, and an overlay
 //    graphic, and we need to be able to set the pattern phase of our background
 //    window.
 // c) We had to be able to support "transparent" themes, so that you could see
@@ skipping 29 matching lines @@
 + (BOOL)drawWindowThemeInDirtyRect:(NSRect)dirtyRect
                            forView:(NSView*)view
                             bounds:(NSRect)bounds
                             offset:(NSPoint)offset
               forceBlackBackground:(BOOL)forceBlackBackground;
 
 // Gets the color to draw title text.
 + (NSColor*)titleColorForThemeView:(NSView*)view;
 
 @end