Honor --gpu-switching=force_discrete to always stay on discrete 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 "base/memory/scoped_generic_obj.h"
@@ skipping 12 matching lines @@
   virtual bool Initialize(GLSurface* compatible_surface,
                           GpuPreference gpu_preference) OVERRIDE;
   virtual void Destroy() OVERRIDE;
   virtual bool MakeCurrent(GLSurface* surface) OVERRIDE;
   virtual void ReleaseCurrent(GLSurface* surface) OVERRIDE;
   virtual bool IsCurrent(GLSurface* surface) OVERRIDE;
   virtual void* GetHandle() OVERRIDE;
   virtual void SetSwapInterval(int interval) OVERRIDE;
   virtual bool GetTotalGpuMemory(size_t* bytes) OVERRIDE;
 
+  // Helper for dual-GPU support on systems where this is necessary
+  // for stability reasons.
+  static void ForceUseOfDiscreteGPU();
+
  protected:
   virtual ~GLContextCGL();
 
  private:
   GpuPreference GetGpuPreference();
 
   void* context_;
   GpuPreference gpu_preference_;
 
   CGLPixelFormatObj discrete_pixelformat_;
 
   DISALLOW_COPY_AND_ASSIGN(GLContextCGL);
 };
 
 class ScopedCGLDestroyRendererInfo {
  public:
   void operator()(CGLRendererInfoObj x) const;
 };
 
 typedef ScopedGenericObj<CGLRendererInfoObj, ScopedCGLDestroyRendererInfo>
     ScopedCGLRendererInfoObj;
 
 }  // namespace gfx
 
 #endif  // UI_GL_GL_CONTEXT_CGL_H_