[Mac] Remove -[NSWindow drawRect] swizzling.

chrome/browser/ui/cocoa/custom_frame_view.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.
 
 #import <Cocoa/Cocoa.h>
 
 // CustomFrameView is a class whose methods we swizzle into NSGrayFrame
 // 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.
+// support custom frame drawing.
 // 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
-//    through to the underlying windows in places without the system theme
-//    getting in the way.
-//
-// Since we want "A" we couldn't just do a transparent borderless window. At
-// least I couldn't find the right combination of HITheme calls to make it draw
-// nicely, and I don't trust that the HITheme calls are going to exist in future
-// system versions.
-// "C" precluded us from inserting a view between the system frame and the
-// the content frame in Z order. To get the transparency we actually need to
-// replace the drawing of the system frame.
-// "B" precluded us from just setting a background color on the window.
-//
-// Originally we tried overriding the private API +frameViewForStyleMask: to
-// add our own subclass of NSGrayView to our window. Turns out that if you
-// subclass NSGrayView it does not draw correctly when you call NSGrayView's
-// drawRect. It appears that NSGrayView's drawRect: method (and that of its
-// superclasses) do lots of "isMemberOfClass/isKindOfClass" calls, and if your
-// class is NOT an instance of NSGrayView (as opposed to a subclass of
-// NSGrayView) then the system drawing will not work correctly.
-//
-// Given all of the above, we found swizzling drawRect in _load to be the
-// easiest and safest method of achieving our goals. We do the best we can to
-// check that everything is safe, and attempt to fallback gracefully if it is
-// not.
-
-@interface NSWindow (CustomFrameView)
-
-// To define custom window drawing behaviour, override this method on an
-// NSWindow subclass. Call the default method (on super) to draw the
-// default frame.
-// NOTE: Always call the default implementation (even if you just immediately
-// draw over it), otherwise the top-left and top-right corners of the window
-// won't be drawn correctly.
-- (void)drawCustomFrameRect:(NSRect)rect forView:(NSView*)view;
-
-@end
-
 
 @interface NSView (CustomFrameView)
 
 // Returns where the fullscreen button's origin should be positioned in window
 // coordinates.
 // We swizzle NSThemeFrame's implementation to center it vertically in the
 // tabstrip (if there is a tabstrip), and to shift it to the left of the
 // old-style avatar icon if necessary.
 - (NSPoint)_fullScreenButtonOrigin;
 
 @end