Move code in ui/gl/* from gfx:: to gl::

ui/gl/gpu_preference.h

 // 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.
 
 #ifndef UI_GL_GPU_PREFERENCE_H_
 #define UI_GL_GPU_PREFERENCE_H_
 
-namespace gfx {
+namespace gl {
 
 // On dual-GPU systems, expresses a preference for using the integrated
 // or discrete GPU. On systems that have dual-GPU support (see
 // GpuDataManagerImpl), 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,
   GpuPreferenceLast = PreferDiscreteGpu
 };
 
-}  // namespace gfx
+}  // namespace gl
 
 #endif  // UI_GL_GPU_PREFERENCE_H_