Update from chromium https://crrev.com/301315

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 a097d9af681e1b9476bc059b6009d460fdcda72d..7e82d62481852762f55e091d3783acc92fb2922e 100644
--- a/ui/gl/gpu_switching_manager.h
+++ b/ui/gl/gpu_switching_manager.h
@@ -8,8 +8,10 @@
 #include <vector>
 
 #include "base/memory/singleton.h"
+#include "base/observer_list.h"
 #include "ui/gl/gl_export.h"
 #include "ui/gl/gpu_preference.h"
+#include "ui/gl/gpu_switching_observer.h"
 
 #if defined(OS_MACOSX)
 #include <OpenGL/OpenGL.h>
@@ -40,6 +42,16 @@ class GL_EXPORT GpuSwitchingManager {
 
   void SetGpuCount(size_t gpu_count);
 
+  void AddObserver(GpuSwitchingObserver* observer);
+  void RemoveObserver(GpuSwitchingObserver* observer);
+
+  // Called when a GPU switch is noticed by the system. In the browser process
+  // this is occurs as a result of a system observer. In the GPU process, this
+  // occurs as a result of an IPC from the browser. The system observer is kept
+  // in the browser process only so that any workarounds or blacklisting can
+  // be applied there.
+  void NotifyGpuSwitched();
+
  private:
   friend struct DefaultSingletonTraits<GpuSwitchingManager>;
 
@@ -60,6 +72,8 @@ class GL_EXPORT GpuSwitchingManager {
 
   size_t gpu_count_;
 
+  ObserverList<GpuSwitchingObserver> observer_list_;
+
   DISALLOW_COPY_AND_ASSIGN(GpuSwitchingManager);
 };