Set USE(NEW_THEME) in config.h instead of a gyp file

Source/core/rendering/RenderTheme.h

 /*
  * This file is part of the theme implementation for form controls in WebCore.
  *
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Computer, 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,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #ifndef RenderTheme_h
 #define RenderTheme_h
 
+#if OS(DARWIN)
+#define WTF_USE_NEW_THEME 1
+#endif

[abarth-chromium, 2013/08/12 19:43:21]

This should got in Platform.h rather than here.  We assume that USE macros a
visible globally in the project.

[lgombos, 2013/08/13 14:52:45]

It seems to me that from the ~20 USE() guards currently in Blink, most of the
guards are only used under core/ (layers on top of wtf/) and many are already
set/scoped so that they are not visible under wtf/ (WEBAUDIO_XX,
NATIVE_FULLSCREEN_VIDEO, CONCATENATED_IMPULSE_RESPONSES, etc.).

The only macro I've found that is used both under wtf/ and core/ is USE(CF), the
rest seems to be only used either under wtf/ or layers above wtf/.

We also seem to be inconsistent abut whether these macros are set in .h files or
in .gyp* files. Many are set in core/features.gypi and many in Platform.h. My
understanding was that we should aim to eliminate Platform.h in the hope of
gaining on build times.
  
I see value in scoping these macros to be either just for wtf/ or for layers
above wtf (and perhaps revisit the one/few macros that are used in both layers).

Thoughts ? 

+
 #include "core/platform/ScrollTypes.h"
 #if USE(NEW_THEME)
 #include "core/platform/Theme.h"
 #else
 #include "core/platform/ThemeTypes.h"
 #endif
 #include "core/rendering/RenderObject.h"
 #include "core/rendering/style/CachedUAStyle.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
@@ skipping 320 matching lines @@
     static const RGBA32 defaultTapHighlightColor = 0x66000000;
 
 #if USE(NEW_THEME)
     Theme* m_theme; // The platform-specific theme.
 #endif
 };
 
 } // namespace WebCore
 
 #endif // RenderTheme_h