Several minor improvements of DirectX capturer

webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc

Index: webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc
diff --git a/webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc b/webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc
index d7eb335fc3cf1e193da07b977424a38920b2fe6f..7dcbbb2db6c7af1038dd3517acc6406146859f8f 100644
--- a/webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc
+++ b/webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc
@@ -147,7 +147,9 @@ bool DxgiOutputDuplicator::Duplicate(Context* context,
   // after it has been merged to updated_region.
   DesktopRegion updated_region;
   updated_region.Swap(&context->updated_region);
-  if (error.Error() == S_OK && frame_info.AccumulatedFrames > 0) {
+  if (error.Error() == S_OK &&
+      frame_info.AccumulatedFrames > 0 &&
+      resource) {

[Jamie, 2016/09/17 00:49:30]

Please add something to the CL description for this change.

[Hzj_jie, 2016/09/19 19:09:57]

Done.

     DetectUpdatedRegion(frame_info, offset, &context->updated_region);
     if (!texture_->CopyFrom(frame_info, resource.Get(),
                             context->updated_region)) {