Prevent browser thumbnailer from trying to read from frontbuffer (surface texture) when none exists.

content/browser/renderer_host/render_widget_host_view_aura.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/browser/renderer_host/render_widget_host_view_aura.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/logging.h"
@@ skipping 315 matching lines @@
 }
 
 void RenderWidgetHostViewAura::Blur() {
   window_->Blur();
 }
 
 bool RenderWidgetHostViewAura::HasFocus() const {
   return window_->HasFocus();
 }
 
+bool RenderWidgetHostViewAura::IsSurfaceAvailableForCopy() const {
+  return current_surface_ != 0;
+}
+
 void RenderWidgetHostViewAura::Show() {
   window_->Show();
 }
 
 void RenderWidgetHostViewAura::Hide() {
   window_->Hide();
 }
 
 bool RenderWidgetHostViewAura::IsShowing() {
   return window_->IsVisible();
@@ skipping 96 matching lines @@
 
 void RenderWidgetHostViewAura::CopyFromCompositingSurface(
     const gfx::Size& size,
     skia::PlatformCanvas* output,
     base::Callback<void(bool)> callback) {
   base::ScopedClosureRunner scoped_callback_runner(base::Bind(callback, false));
   ui::Compositor* compositor = GetCompositor();
   if (!compositor)
     return;
 
-  ImageTransportClient* container = image_transport_clients_[current_surface_];
-  if (!container)
+  std::map<uint64, scoped_refptr<ImageTransportClient> >::iterator it =
+      image_transport_clients_.find(current_surface_);
+  if (it == image_transport_clients_.end())
     return;
 
+  ImageTransportClient* container = it->second;
+  DCHECK(container);
+
   gfx::Size size_in_pixel = content::ConvertSizeToPixel(this, size);
   if (!output->initialize(
       size_in_pixel.width(), size_in_pixel.height(), true))
     return;
 
   ImageTransportFactory* factory = ImageTransportFactory::GetInstance();
   content::GLHelper* gl_helper = factory->GetGLHelper(compositor);
   if (!gl_helper)
     return;
 
@@ skipping 861 matching lines @@
 RenderWidgetHostView* RenderWidgetHostView::CreateViewForWidget(
     RenderWidgetHost* widget) {
   return new RenderWidgetHostViewAura(widget);
 }
 
 // static
 void content::RenderWidgetHostViewPort::GetDefaultScreenInfo(
     WebKit::WebScreenInfo* results) {
   GetScreenInfoForWindow(results, NULL);
 }