Refactor how surfaces are acquired for GPU compositing.

chrome/browser/renderer_host/render_widget_host_view_mac.mm

Index: chrome/browser/renderer_host/render_widget_host_view_mac.mm
diff --git a/chrome/browser/renderer_host/render_widget_host_view_mac.mm b/chrome/browser/renderer_host/render_widget_host_view_mac.mm
index 693b62972f996fe29c7729ef1512c73af9740df5..0d1e29b2ac7a8d6054190a120c0652a2023a43ea 100644
--- a/chrome/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/chrome/browser/renderer_host/render_widget_host_view_mac.mm
@@ -1205,6 +1205,15 @@ void RenderWidgetHostViewMac::GpuRenderingStateDidChange() {
   }
 }
 
+gfx::PluginWindowHandle RenderWidgetHostViewMac::AcquireCompositingSurface() {
+  return AllocateFakePluginWindowHandle(/*opaque=*/true, /*root=*/true);
+}
+
+void RenderWidgetHostViewMac::ReleaseCompositingSurface(
+    gfx::PluginWindowHandle surface) {
+  DestroyFakePluginWindowHandle(surface);
+}
+
 void RenderWidgetHostViewMac::DrawAcceleratedSurfaceInstance(
       CGLContextObj context,
       gfx::PluginWindowHandle plugin_handle,