Allow CopyFromBackingStore to fallback to copying from the renderer side if the accelerated surface…

content/browser/renderer_host/media/web_contents_video_capture_device.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.
 //
 // Implementation notes: This needs to work on a variety of hardware
 // configurations where the speed of the CPU and GPU greatly affect overall
 // performance. Spanning several threads, the process of capturing has been
 // split up into four conceptual stages:
 //
 //   1. Reserve Buffer: Before a frame can be captured, a slot in the consumer's
@@ skipping 971 matching lines @@
       // Measure the number of kilopixels.
       UMA_HISTOGRAM_COUNTS_10000(
           "TabCapture.ViewChangeKiloPixels",
           view_size.width() * view_size.height() / 1024);
     }
   }
 
   TRACE_EVENT_ASYNC_BEGIN1("mirroring", "Capture", this,
                            "frame_number", frame_number);
 
-  if (view && view->CanCopyToVideoFrame()) {
+  if (!view->IsSurfaceAvailableForCopy()) {
+    // Fallback to the more expensive renderer-side copy if the surface and
+    // backing store are not accessible.
+    rwh->GetSnapshotFromRenderer(
+        gfx::Rect(),
+        base::Bind(&BackingStoreCopier::DidCopyFromBackingStore,
+                   base::Unretained(this), frame_number,
+                   base::Time::Now(), callback));
+  } else if (view && view->CanCopyToVideoFrame()) {
     gfx::Size view_size = view->GetViewBounds().size();
 
     view->CopyFromCompositingSurfaceToVideoFrame(
         gfx::Rect(view_size),
         target,
         base::Bind(
             &BackingStoreCopier::DidCopyFromCompositingSurfaceToVideoFrame,
             base::Unretained(this), frame_number,
             base::Time::Now(), callback));
   } else {
@@ skipping 109 matching lines @@
   capturer_->SetConsumer(NULL);
   capturer_->DeAllocate();
 }
 
 const media::VideoCaptureDevice::Name&
 WebContentsVideoCaptureDevice::device_name() {
   return device_name_;
 }
 
 }  // namespace content