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 943c8cc64a5b8566afd8b83569fcaec1a0b74222..4bb8f77d94ea4b138102d61fd93265cc7626b9c2 100644
--- a/chrome/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/chrome/browser/renderer_host/render_widget_host_view_mac.mm
@@ -1247,6 +1247,15 @@ 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,