Add a user pref in Settings to disable all GPU features.

chrome/chrome_browser.gypi

 # Copyright 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.
 
 {
   'targets': [
     {
       'target_name': 'browser',
       'type': 'static_library',
       'variables': { 'enable_wexit_time_destructors': 1, },
@@ skipping 712 matching lines @@
         'browser/google_apis/task_util.cc',
         'browser/google_apis/task_util.h',
         'browser/google_apis/time_util.cc',
         'browser/google_apis/time_util.h',
         'browser/gpu/chrome_gpu_util.cc',
         'browser/gpu/chrome_gpu_util.h',
         'browser/gpu/gl_string_manager.cc',
         'browser/gpu/gl_string_manager.h',
         'browser/gpu/gpu_feature_checker.cc',
         'browser/gpu/gpu_feature_checker.h',
+        'browser/gpu/gpu_mode_manager.cc',
+        'browser/gpu/gpu_mode_manager.h',
         'browser/hang_monitor/hang_crash_dump_win.cc',
         'browser/hang_monitor/hang_crash_dump_win.h',
         'browser/hang_monitor/hung_plugin_action.cc',
         'browser/hang_monitor/hung_plugin_action.h',
         'browser/hang_monitor/hung_window_detector.cc',
         'browser/hang_monitor/hung_window_detector.h',
         'browser/history/android/android_cache_database.cc',
         'browser/history/android/android_cache_database.h',
         'browser/history/android/android_history_provider_service.cc',
         'browser/history/android/android_history_provider_service.h',
@@ skipping 2423 matching lines @@
             'package_name': 'org/chromium/chrome/browser/ui/toolbar',
             'template_deps': ['browser/ui/toolbar/toolbar_model_security_level_list.h'],
           },
           'includes': [ '../build/android/java_cpp_template.gypi' ],
         },
       ],
      },
     ],
   ],
 }