Refactor how surfaces are acquired for GPU compositing.

chrome/browser/renderer_host/render_widget_host_view_win.cc

Index: chrome/browser/renderer_host/render_widget_host_view_win.cc
diff --git a/chrome/browser/renderer_host/render_widget_host_view_win.cc b/chrome/browser/renderer_host/render_widget_host_view_win.cc
index 459b9e526afd63692b4551d1c752b617dc0d1ed7..ab5de6b32a7016943761bd1178e8fafb339ce51d 100644
--- a/chrome/browser/renderer_host/render_widget_host_view_win.cc
+++ b/chrome/browser/renderer_host/render_widget_host_view_win.cc
@@ -1546,7 +1546,7 @@ static LRESULT CALLBACK CompositorHostWindowProc(HWND hWnd, UINT message,
 // Creates a HWND within the RenderWidgetHostView that will serve as a host
 // for a HWND that the GPU process will create. The host window is used
 // to Z-position the GPU's window relative to other plugin windows.
-gfx::PluginWindowHandle RenderWidgetHostViewWin::GetCompositorHostWindow() {
+gfx::PluginWindowHandle RenderWidgetHostViewWin::AcquireCompositingSurface() {
   // If the window has been created, don't recreate it a second time
   if (compositor_host_window_)
     return compositor_host_window_;
@@ -1585,6 +1585,11 @@ gfx::PluginWindowHandle RenderWidgetHostViewWin::GetCompositorHostWindow() {
   return static_cast<gfx::PluginWindowHandle>(compositor_host_window_);
 }
 
+void RenderWidgetHostViewWin::ReleaseCompositingSurface(
+    gfx::PluginWindowHandle surface) {
+  ShowCompositorHostWindow(false);
+}
+
 void RenderWidgetHostViewWin::ShowCompositorHostWindow(bool show) {
   // When we first create the compositor, we will get a show request from
   // the renderer before we have gotten the create request from the GPU. In this