Refine dual-GPU detection on Mac OS X.

ui/gl/gpu_switching_manager.h

Index: ui/gl/gpu_switching_manager.h
diff --git a/ui/gl/gpu_switching_manager.h b/ui/gl/gpu_switching_manager.h
index a6a810f8bf1473ec31b1926db0ce7c4a60ab1b4f..3f1acc222541f045a1fc2e0db87977ac7435c0e9 100644
--- a/ui/gl/gpu_switching_manager.h
+++ b/ui/gl/gpu_switching_manager.h
@@ -36,7 +36,9 @@ class GL_EXPORT GpuSwitchingManager {
   // --supports-dual-gpus commandline switch.
   bool SupportsDualGpus();
 
-  void SetGpuCount(size_t gpu_count);
+  // Sets the vendor IDs of the GPUs on the system. The length of this
+  // vector defines the count of GPUs.
+  void SetGpuVendorIds(const std::vector<uint32>& vendor_ids);
 
   void AddObserver(GpuSwitchingObserver* observer);
   void RemoveObserver(GpuSwitchingObserver* observer);
@@ -61,11 +63,11 @@ class GL_EXPORT GpuSwitchingManager {
   gfx::GpuPreference gpu_switching_option_;
   bool gpu_switching_option_set_;
 
+  std::vector<uint32> vendor_ids_;
+
   bool supports_dual_gpus_;
   bool supports_dual_gpus_set_;
 
-  size_t gpu_count_;
-
   struct PlatformSpecific;
   scoped_ptr<PlatformSpecific> platform_specific_;