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 896862b58d16c3e45da6efa99f8b7e2020ea4b9f..cac04a02942c56f5c88f5ea88b935ac2397f2991 100644
--- a/chrome/browser/renderer_host/render_widget_host_view_win.cc
+++ b/chrome/browser/renderer_host/render_widget_host_view_win.cc
@@ -1545,7 +1545,7 @@ 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_;
@@ -1584,6 +1584,11 @@ 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