Fix bug whereby OnGpuSwitched was never called

gpu/config/gpu_info.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 GPU_CONFIG_GPU_INFO_H_
 #define GPU_CONFIG_GPU_INFO_H_
 
 // Provides access to the GPU information for the system
 // on which chrome is currently running.
 
@@ skipping 125 matching lines @@
 
   // Computer has AMD Dynamic Switchable Graphics
   bool amd_switchable;
 
   // Primary GPU, for exmaple, the discrete GPU in a dual GPU machine.
   GPUDevice gpu;
 
   // Secondary GPUs, for example, the integrated GPU in a dual GPU machine.
   std::vector<GPUDevice> secondary_gpus;
 
+  // The currently active gpu.
+  const GPUDevice& active_gpu() const;
+
   // The vendor of the graphics driver currently installed.
   std::string driver_vendor;
 
   // The version of the graphics driver currently installed.
   std::string driver_version;
 
   // The date of the graphics driver currently installed.
   std::string driver_date;
 
   // The version of the pixel/fragment shader used by the gpu.
@@ skipping 128 matching lines @@
     virtual ~Enumerator() {}
   };
 
   // Outputs the fields in this structure to the provided enumerator.
   void EnumerateFields(Enumerator* enumerator) const;
 };
 
 }  // namespace gpu
 
 #endif  // GPU_CONFIG_GPU_INFO_H_