Fix lost context race with fullscreen pepper widget.

content/renderer/render_widget_fullscreen_pepper.cc

 // Copyright (c) 2011 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_fullscreen_pepper.h"
 
 #include "base/message_loop.h"
 #include "content/common/view_messages.h"
 #include "content/renderer/gpu/gpu_channel_host.h"
 #include "content/renderer/pepper_platform_context_3d_impl.h"
@@ skipping 444 matching lines @@
   gl->BufferData(GL_ARRAY_BUFFER,
                  sizeof(kTexCoords),
                  kTexCoords,
                  GL_STATIC_DRAW);
   gl->VertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, NULL);
   gl->EnableVertexAttribArray(0);
   return true;
 }
 
 bool RenderWidgetFullscreenPepper::CheckCompositing() {
-  bool compositing = webwidget_->isAcceleratedCompositingActive();
-  if (compositing != is_accelerated_compositing_active_) {
+  bool compositing =
+      webwidget_ && webwidget_->isAcceleratedCompositingActive();
+  if (compositing != is_accelerated_compositing_active_)
     didActivateAcceleratedCompositing(compositing);
-  }
   return compositing;
 }
 
 void RenderWidgetFullscreenPepper::SwapBuffers() {
   DCHECK(context_);
   OnSwapBuffersPosted();
   context_->SwapBuffers();
 }
 
 void RenderWidgetFullscreenPepper::OnLostContext(
     RendererGLContext::ContextLostReason) {
   if (!context_)
     return;
   // Destroy the context later, in case we got called from InitContext for
   // example. We still need to reset context_ now so that a new context gets
   // created when the plugin recreates its own.
   MessageLoop::current()->PostTask(
       FROM_HERE,
       NewRunnableFunction(DestroyContext, context_, program_, buffer_));
   context_ = NULL;
   program_ = 0;
   buffer_ = 0;
   OnSwapBuffersAborted();
+  CheckCompositing();
 }
 
 void RenderWidgetFullscreenPepper::OnSwapBuffersCompleteByRendererGLContext() {
   OnSwapBuffersComplete();
 }