Make SingleThreadProxy a SchedulerClient

content/renderer/render_widget.cc

Index: content/renderer/render_widget.cc
diff --git a/content/renderer/render_widget.cc b/content/renderer/render_widget.cc
index 73ab00862d967b0b3e2574d512c08cb8397fe76c..0b67c25c5097b56dee79c7081a3520a27fe90bbd 100644
--- a/content/renderer/render_widget.cc
+++ b/content/renderer/render_widget.cc
@@ -386,6 +386,7 @@ RenderWidget::RenderWidget(blink::WebPopupType popup_type,
       handling_event_type_(WebInputEvent::Undefined),
       ignore_ack_for_mouse_move_from_debugger_(false),
       closing_(false),
+      host_closing_(false),
       is_swapped_out_(swapped_out),
       input_method_is_active_(false),
       text_input_type_(ui::TEXT_INPUT_TYPE_NONE),
@@ -1172,6 +1173,11 @@ void RenderWidget::AutoResizeCompositor()  {
 }
 
 void RenderWidget::initializeLayerTreeView() {
+  // The host is currently shutting down and any old compositors  have
+  // been destroyed, so don't create any new ones.
+  if (host_closing_)
+    return;
+
   compositor_ = RenderWidgetCompositor::Create(
       this, is_threaded_compositing_enabled_);
   compositor_->setViewportSize(size_, physical_backing_size_);
@@ -1179,6 +1185,13 @@ void RenderWidget::initializeLayerTreeView() {
     StartCompositor();
 }
 
+void RenderWidget::DestroyLayerTreeView() {
+  if (!compositor_)
+    return;
+  webwidget_->willCloseLayerTreeView();
+  compositor_.reset();
+}
+
 blink::WebLayerTreeView* RenderWidget::layerTreeView() {
   return compositor_.get();
 }
@@ -1191,8 +1204,6 @@ void RenderWidget::suppressCompositorScheduling(bool enable) {
 void RenderWidget::willBeginCompositorFrame() {
   TRACE_EVENT0("gpu", "RenderWidget::willBeginCompositorFrame");
 
-  DCHECK(RenderThreadImpl::current()->compositor_message_loop_proxy().get());
-
   // The following two can result in further layout and possibly
   // enable GPU acceleration so they need to be called before any painting
   // is done.
@@ -1296,6 +1307,12 @@ void RenderWidget::didBlur() {
 }
 
 void RenderWidget::DoDeferredClose() {
+  // No more compositing is possible.  This prevents shutdown races between
+  // previously posted CreateOutputSurface tasks and the host being unable to
+  // create them because the close message was handled.
+  DestroyLayerTreeView();
+  // Also prevent new compositors from being created.
+  host_closing_ = true;
   Send(new ViewHostMsg_Close(routing_id_));
 }
 
@@ -1336,8 +1353,7 @@ void RenderWidget::QueueSyntheticGesture(
 void RenderWidget::Close() {
   screen_metrics_emulator_.reset();
   if (webwidget_) {
-    webwidget_->willCloseLayerTreeView();
-    compositor_.reset();
+    DestroyLayerTreeView();
     webwidget_->close();
     webwidget_ = NULL;
   }