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

ui/gl/gpu_switching_manager.cc

Index: ui/gl/gpu_switching_manager.cc
diff --git a/ui/gl/gpu_switching_manager.cc b/ui/gl/gpu_switching_manager.cc
index 05a7865c6bf03d382841ae41a242d675efa2bfea..f9046291d3a8dbae46a5edb6a92e58d858528d38 100644
--- a/ui/gl/gpu_switching_manager.cc
+++ b/ui/gl/gpu_switching_manager.cc
@@ -102,6 +102,18 @@ void GpuSwitchingManager::SetGpuCount(size_t gpu_count) {
   gpu_count_ = gpu_count;
 }
 
+void GpuSwitchingManager::AddObserver(GpuSwitchingObserver* observer) {
+  observer_list_.AddObserver(observer);
+}
+
+void GpuSwitchingManager::RemoveObserver(GpuSwitchingObserver* observer) {
+  observer_list_.RemoveObserver(observer);
+}
+
+void GpuSwitchingManager::NotifyGpuSwitched() {
+  FOR_EACH_OBSERVER(GpuSwitchingObserver, observer_list_, OnGpuSwitched());
+}
+
 gfx::GpuPreference GpuSwitchingManager::AdjustGpuPreference(
     gfx::GpuPreference gpu_preference) {
   if (!gpu_switching_option_set_)