Clean up mac gpu switching code a little.

content/browser/gpu/gpu_data_manager_impl.h

Index: content/browser/gpu/gpu_data_manager_impl.h
diff --git a/content/browser/gpu/gpu_data_manager_impl.h b/content/browser/gpu/gpu_data_manager_impl.h
index e3e92afca9bf1c311ba6a05108a04907619a551b..5a783e46c75c38d25a968b6c5d8fc2dea1e35257 100644
--- a/content/browser/gpu/gpu_data_manager_impl.h
+++ b/content/browser/gpu/gpu_data_manager_impl.h
@@ -166,6 +166,10 @@ class CONTENT_EXPORT GpuDataManagerImpl
   void SetDisplayCount(unsigned int display_count);
   unsigned int GetDisplayCount() const;
 
+  // Set the active gpu.
+  // Return true if it's a different GPU from the previous active one.
+  bool UpdateActiveGpu(uint32 vendor_id, uint32 device_id);
+
   // Called when GPU process initialization failed.
   void OnGpuProcessInitFailure();