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

ui/gl/gl_context_mac.mm

Index: ui/gl/gl_context_mac.mm
===================================================================
--- ui/gl/gl_context_mac.mm	(revision 156195)
+++ ui/gl/gl_context_mac.mm	(working copy)
@@ -17,6 +17,7 @@
 #include "ui/gl/gl_implementation.h"
 #include "ui/gl/gl_surface.h"
 #include "ui/gl/gl_switches.h"
+#include "ui/gl/gpu_switching_manager.h"
 
 #if defined(USE_AURA)
 #include "ui/gl/gl_context_nsview.h"
@@ -170,7 +171,7 @@
             switches::kDisableGpuSwitching);
 
     if (forcibly_disable) {
-      GLContextCGL::ForceUseOfDiscreteGPU();
+      GpuSwitchingManager::GetInstance()->ForceUseOfDiscreteGpu();
       return false;
     }