Include AvailabilityMacros.h only where it is used.

Source/core/rendering/RenderThemeChromiumMac.mm

 /*
  * Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Google, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 40 matching lines @@
 #import "core/rendering/PaintInfo.h"
 #import "core/rendering/RenderLayer.h"
 #import "core/rendering/RenderMedia.h"
 #import "core/rendering/RenderMediaControls.h"
 #import "core/rendering/RenderMediaControlsChromium.h"
 #import "core/rendering/RenderMeter.h"
 #import "core/rendering/RenderProgress.h"
 #import "core/rendering/RenderSlider.h"
 #import "core/rendering/RenderView.h"
 
+#import <AvailabilityMacros.h>
 #import <Carbon/Carbon.h>
 #import <Cocoa/Cocoa.h>
 #import <math.h>
 #import <wtf/RetainPtr.h>
 #import <wtf/StdLibExtras.h>
 
 using namespace std;
 
 // The methods in this file are specific to the Mac OS X platform.
 
@@ skipping 1894 matching lines @@
 
 bool RenderThemeChromiumMac::shouldUseFallbackTheme(RenderStyle* style) const
 {
     ControlPart part = style->appearance();
     if (part == CheckboxPart || part == RadioPart)
         return style->effectiveZoom() != 1;
     return false;
 }
 
 } // namespace WebCore