Implement blacklist's force GPU capability in dual GPU machines.

ui/gl/gl_switches.cc

 // 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 "ui/gl/gl_switches.h"
 
 namespace gfx {
 
 const char kGLImplementationDesktopName[]     = "desktop";
 const char kGLImplementationOSMesaName[]      = "osmesa";
@@ skipping 30 matching lines @@
 
 // Inform Chrome that a GPU context will not be lost in power saving mode,
 // screen saving mode, etc.  Note that this flag does not ensure that a GPU
 // context will never be lost in any situations, say, a GPU reset.
 const char kGpuNoContextLost[]              = "gpu-no-context-lost";
 
 // Add a delay in milliseconds to the gpu swap buffer completion signal.
 // Simulates a slow GPU.
 const char kGpuSwapDelay[]                  = "gpu-swap-delay";
 
+// Overwrite the default GPU automatic switching behavior to force on
+// integrated GPU or discrete GPU.
+const char kGpuSwitching[]                  = "gpu-switching";
+
 // Flag used for Linux tests: for desktop GL bindings, try to load this GL
 // library first, but fall back to regular library if loading fails.
 const char kTestGLLib[]                     = "test-gl-lib";
 
 }  // namespace switches