Several minor improvements of DirectX capturer

webrtc/modules/desktop_capture/win/dxgi_adapter_duplicator.cc

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 44 matching lines @@
 
     if (error.Error() != S_OK || !output) {
       LOG(LS_WARNING) << "IDXGIAdapter::EnumOutputs returns an unexpected "
                          "result "
                       << error.ErrorMessage() << " with error code"
                       << error.Error();
       return false;
     }
 
     DXGI_OUTPUT_DESC desc;
-    error = _com_error(output->GetDesc(&desc));
+    error = output->GetDesc(&desc);
     if (error.Error() == S_OK) {
       if (desc.AttachedToDesktop && IsValidRect(desc.DesktopCoordinates)) {
         ComPtr<IDXGIOutput1> output1;
-        error = _com_error(output.As(&output1));
+        error = output.As(&output1);
         if (error.Error() != S_OK || !output1) {
           LOG(LS_WARNING) << "Failed to convert IDXGIOutput to IDXGIOutput1, "
                              "this usually means the system does not support "
                              "DirectX 11";
           return false;
         }
         duplicators_.emplace_back(device_, output1, desc);
         if (!duplicators_.back().Initialize()) {
           return false;
         }
@@ skipping 54 matching lines @@
   return duplicators_[monitor_id].Duplicate(&context->contexts[monitor_id],
                                             DesktopVector(), target);
 }
 
 DesktopRect DxgiAdapterDuplicator::ScreenRect(int id) const {
   RTC_DCHECK(id >= 0 && id < static_cast<int>(duplicators_.size()));
   return duplicators_[id].desktop_rect();
 }
 
 }  // namespace webrtc