Support dynamic switching between integrated and discrete GPUs on Mac OS X.

ui/gfx/gl/gpu_preference.h

+// Copyright (c) 2011 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.
+
+#ifndef UI_GFX_GL_GPU_PREFERENCE_H_
+#define UI_GFX_GL_GPU_PREFERENCE_H_
+#pragma once
+
+namespace gfx {
+
+// On dual-GPU systems, expresses a preference for using the integrated
+// or discrete GPU. On systems that have dual-GPU support (see
+// GLContext::SupportsDualGpus), resource sharing only works between
+// contexts that are created with the same GPU preference.
+//
+// This API will likely need to be adjusted as the functionality is
+// implemented on more operating systems.
+enum GpuPreference {
+  PreferIntegratedGpu,
+  PreferDiscreteGpu
+};
+
+}  // namespace gfx
+
+#endif  // UI_GFX_GL_GPU_PREFERENCE_H_