Use GpuPreferences to avoid directly accessing switches in gpu related code

gpu/command_buffer_service.gypi

 # 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_dirs': [
     '..',
   ],
   'all_dependent_settings': {
     'include_dirs': [
@@ skipping 48 matching lines @@
     'command_buffer/service/gles2_cmd_clear_framebuffer.h',
     'command_buffer/service/gles2_cmd_copy_texture_chromium.cc',
     'command_buffer/service/gles2_cmd_copy_texture_chromium.h',
     'command_buffer/service/gles2_cmd_decoder.cc',
     'command_buffer/service/gles2_cmd_decoder.h',
     'command_buffer/service/gles2_cmd_decoder_autogen.h',
     'command_buffer/service/gles2_cmd_validation.cc',
     'command_buffer/service/gles2_cmd_validation.h',
     'command_buffer/service/gles2_cmd_validation_autogen.h',
     'command_buffer/service/gles2_cmd_validation_implementation_autogen.h',
+    'command_buffer/service/gpu_preferences.cc',
+    'command_buffer/service/gpu_preferences.h',
     'command_buffer/service/gpu_scheduler.cc',
     'command_buffer/service/gpu_scheduler.h',
     'command_buffer/service/gpu_state_tracer.cc',
     'command_buffer/service/gpu_state_tracer.h',
     'command_buffer/service/gpu_switches.cc',
     'command_buffer/service/gpu_switches.h',
     'command_buffer/service/gpu_tracer.cc',
     'command_buffer/service/gpu_tracer.h',
     'command_buffer/service/id_manager.cc',
     'command_buffer/service/id_manager.h',
@@ skipping 59 matching lines @@
       # Required by gles2_cmd_decoder.cc on Mac.
       'link_settings': {
         'libraries': [
           '$(SDKROOT)/System/Library/Frameworks/IOSurface.framework',
           '$(SDKROOT)/System/Library/Frameworks/OpenGL.framework',
         ],
       },
     }],
   ],
 }