Fix swapbuffers accounting in single-threaded mode

content/renderer/render_widget.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/render_widget.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
@@ skipping 1098 matching lines @@
   }
 
   // Suppress updating when we are hidden.
   if (is_hidden_ || size_.IsEmpty() || is_swapped_out_) {
     paint_aggregator_.ClearPendingUpdate();
     needs_repainting_on_restore_ = true;
     TRACE_EVENT0("renderer", "EarlyOut_NotVisible");
     return;
   }
 
-  if (is_accelerated_compositing_active_)
-    using_asynchronous_swapbuffers_ = SupportsAsynchronousSwapBuffers();
-
   // Tracking of frame rate jitter
   base::TimeTicks frame_begin_ticks = base::TimeTicks::Now();
   InstrumentWillBeginFrame();
   AnimateIfNeeded();
 
   // Layout may generate more invalidation.  It may also enable the
   // GPU acceleration, so make sure to run layout before we send the
   // 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.
   UpdateTextInputState(DO_NOT_SHOW_IME);
   UpdateSelectionBounds();
 
   // Suppress painting if nothing is dirty.  This has to be done after updating
   // animations running layout as these may generate further invalidations.
   if (!paint_aggregator_.HasPendingUpdate()) {
     TRACE_EVENT0("renderer", "EarlyOut_NoPendingUpdate");
@@ skipping 1251 matching lines @@
 
   if (!context->Initialize(
           attributes,
           false /* bind generates resources */,
           CAUSE_FOR_GPU_LAUNCH_WEBGRAPHICSCONTEXT3DCOMMANDBUFFERIMPL_INITIALIZE))
     return NULL;
   return context.release();
 }
 
 }  // namespace content