Migrate WebGL contexts on backgrounded tabs to the integrated GPU.

ui/gl/gl_context_cgl.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_GL_CONTEXT_CGL_H_
 #define UI_GL_GL_CONTEXT_CGL_H_
 
 #include <OpenGL/CGLTypes.h>
 
 #include <memory>
@@ skipping 15 matching lines @@
   bool Initialize(GLSurface* compatible_surface,
                   const GLContextAttribs& attribs) override;
   bool MakeCurrent(GLSurface* surface) override;
   void ReleaseCurrent(GLSurface* surface) override;
   bool IsCurrent(GLSurface* surface) override;
   void* GetHandle() override;
   void OnSetSwapInterval(int interval) override;
   void SetSafeToForceGpuSwitch() override;
   bool ForceGpuSwitchIfNeeded() override;
   YUVToRGBConverter* GetYUVToRGBConverter() override;
+  void SetPerformancePreference(GpuPerformancePreference pref) override;
 
  protected:
   ~GLContextCGL() override;
 
  private:
   void Destroy();
   GpuPreference GetGpuPreference();
 
+  bool AllocateDiscretePixelFormat();
+  void ReleaseDiscretePixelFormat();
+
   void* context_;
   GpuPreference gpu_preference_;
   std::unique_ptr<YUVToRGBConverter> yuv_to_rgb_converter_;
 
   CGLPixelFormatObj discrete_pixelformat_;
 
   int screen_;
   int renderer_id_;
   bool safe_to_force_gpu_switch_;
 
   DISALLOW_COPY_AND_ASSIGN(GLContextCGL);
 };
 
 }  // namespace gl
 
 #endif  // UI_GL_GL_CONTEXT_CGL_H_