Remove windows/mac/ios specific code from //ui

ui/gl/gl_context_mac.mm

-// 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.
-
-#include "base/basictypes.h"
-#include "base/logging.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/trace_event/trace_event.h"
-#include "ui/gl/gl_context_cgl.h"
-#include "ui/gl/gl_context_osmesa.h"
-#include "ui/gl/gl_context_stub.h"
-#include "ui/gl/gl_implementation.h"
-#include "ui/gl/gl_surface.h"
-#include "ui/gl/gl_switches.h"
-
-namespace gfx {
-
-class GLShareGroup;
-
-scoped_refptr<GLContext> GLContext::CreateGLContext(
-    GLShareGroup* share_group,
-    GLSurface* compatible_surface,
-    GpuPreference gpu_preference) {
-  TRACE_EVENT0("gpu", "GLContext::CreateGLContext");
-  switch (GetGLImplementation()) {
-    case kGLImplementationDesktopGL:
-    case kGLImplementationAppleGL: {
-      scoped_refptr<GLContext> context;
-      // Note that with virtualization we might still be able to make current
-      // a different onscreen surface with this context later. But we should
-      // always be creating the context with an offscreen surface first.
-      DCHECK(compatible_surface->IsOffscreen());
-      context = new GLContextCGL(share_group);
-      if (!context->Initialize(compatible_surface, gpu_preference))
-        return NULL;
-
-      return context;
-    }
-    case kGLImplementationOSMesaGL: {
-      scoped_refptr<GLContext> context(new GLContextOSMesa(share_group));
-      if (!context->Initialize(compatible_surface, gpu_preference))
-        return NULL;
-
-      return context;
-    }
-    case kGLImplementationMockGL:
-      return new GLContextStub;
-    default:
-      NOTREACHED();
-      return NULL;
-  }
-}
-
-}  // namespace gfx