Fix swapbuffers accounting in single-threaded mode

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 11ffaca56e691c49ff0a37d63b028890770added..ccebd13e0e77075e85618009715eb246ca95ef6d 100644
--- a/content/renderer/render_widget.cc
+++ b/content/renderer/render_widget.cc
@@ -1116,9 +1116,6 @@ void RenderWidget::DoDeferredUpdate() {
     return;
   }
 
-  if (is_accelerated_compositing_active_)
-    using_asynchronous_swapbuffers_ = SupportsAsynchronousSwapBuffers();
-
   // Tracking of frame rate jitter
   base::TimeTicks frame_begin_ticks = base::TimeTicks::Now();
   InstrumentWillBeginFrame();
@@ -1129,6 +1126,11 @@ void RenderWidget::DoDeferredUpdate() {
   // GpuRenderingActivated message.
   webwidget_->layout();
 
+  // Check for whether we need to track swap buffers. We need to do that after
+  // layout() because it may have switched us to accelerated compositing.
+  if (is_accelerated_compositing_active_)
+    using_asynchronous_swapbuffers_ = SupportsAsynchronousSwapBuffers();
+
   // The following two can result in further layout and possibly
   // enable GPU acceleration so they need to be called before any painting
   // is done.