Add helpers for CGL types.

ui/gl/cgl_util.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 "base/logging.h"
+#include "ui/gl/cgl_util.h"
+
+namespace gfx {
+
+ScopedCGLSetCurrentContext::ScopedCGLSetCurrentContext(CGLContextObj context)
+    : previous_context_(CGLGetCurrentContext(), base::scoped_policy::RETAIN) {
+  CGLError error = CGLSetCurrentContext(context);
+  DCHECK_EQ(error, kCGLNoError) << "CGLSetCurrentContext should never fail";
+}
+
+ScopedCGLSetCurrentContext::~ScopedCGLSetCurrentContext() {
+  CGLError error = CGLSetCurrentContext(previous_context_);
+  DCHECK_EQ(error, kCGLNoError) << "CGLSetCurrentContext should never fail";
+}
+
+}  // namespace gfx