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 93efaa57403be643d9883fe54cf409cb77e6ae52..82124033ed4dee1007fdc9d174ca29d80c863f93 100644
--- a/content/renderer/render_widget.cc
+++ b/content/renderer/render_widget.cc
@@ -377,6 +377,7 @@ 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),
@@ -1165,6 +1166,11 @@ 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_)

[danakj, 2014/07/02 21:31:42]

Do you think this can/should be a DCHECK one day? If you do can you TODO that it
should be?

[enne (OOO), 2014/07/10 20:37:42]

Done.

+    return;
+
   compositor_ = RenderWidgetCompositor::Create(
       this, is_threaded_compositing_enabled_);
   compositor_->setViewportSize(size_, physical_backing_size_);
@@ -1172,6 +1178,13 @@ void RenderWidget::initializeLayerTreeView() {
     StartCompositor();
 }
 
+void RenderWidget::DestroyLayerTreeView() {
+  if (!compositor_)
+    return;
+  webwidget_->willCloseLayerTreeView();
+  compositor_.reset();
+}
+
 blink::WebLayerTreeView* RenderWidget::layerTreeView() {
   return compositor_.get();
 }
@@ -1184,8 +1197,6 @@ 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.
@@ -1289,6 +1300,12 @@ 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();

[enne (OOO), 2014/07/02 21:19:43]

This is the Chromium side of preventing the race that's described in
https://codereview.chromium.org/362403003/.

+  // Also prevent new compositors from being created.
+  host_closing_ = true;
   Send(new ViewHostMsg_Close(routing_id_));
 }
 
@@ -1328,8 +1345,7 @@ void RenderWidget::QueueSyntheticGesture(
 
 void RenderWidget::Close() {
   if (webwidget_) {
-    webwidget_->willCloseLayerTreeView();
-    compositor_.reset();
+    DestroyLayerTreeView();
     webwidget_->close();
     webwidget_ = NULL;
   }