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

ui/gl/gl_fence_apple.cc

-// Copyright 2014 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 "ui/gl/gl_fence_apple.h"
-
-#include "ui/gl/gl_bindings.h"
-
-namespace gfx {
-
-GLFenceAPPLE::GLFenceAPPLE() {
-  glGenFencesAPPLE(1, &fence_);
-  glSetFenceAPPLE(fence_);
-  DCHECK(glIsFenceAPPLE(fence_));
-  glFlush();
-}
-
-bool GLFenceAPPLE::HasCompleted() {
-  DCHECK(glIsFenceAPPLE(fence_));
-  return !!glTestFenceAPPLE(fence_);
-}
-
-void GLFenceAPPLE::ClientWait() {
-  DCHECK(glIsFenceAPPLE(fence_));
-  glFinishFenceAPPLE(fence_);
-}
-
-void GLFenceAPPLE::ServerWait() {
-  DCHECK(glIsFenceAPPLE(fence_));
-  ClientWait();
-}
-
-GLFenceAPPLE::~GLFenceAPPLE() {
-  DCHECK(glIsFenceAPPLE(fence_));
-  glDeleteFencesAPPLE(1, &fence_);
-}
-
-}  // namespace gfx