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

ui/gl/gpu_switching_manager.cc

 // 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.
 
 #include "ui/gl/gpu_switching_manager.h"
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "ui/gl/gl_switches.h"
 
@@ skipping 84 matching lines @@
     supports_dual_gpus_ = flag;
     supports_dual_gpus_set_ = true;
   }
   return supports_dual_gpus_;
 }
 
 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_)
     return gpu_preference;
   return gpu_switching_option_;
 }
 
 #if defined(OS_MACOSX)
 void GpuSwitchingManager::SwitchToDiscreteGpuMac() {
   if (discrete_pixel_format_)
     return;
   CGLPixelFormatAttribute attribs[1];
   attribs[0] = static_cast<CGLPixelFormatAttribute>(0);
   GLint num_pixel_formats = 0;
   CGLChoosePixelFormat(attribs, &discrete_pixel_format_, &num_pixel_formats);
 }
 #endif  // OS_MACOSX
 
 }  // namespace ui