Several minor improvements of DirectX capturer

webrtc/modules/desktop_capture/win/d3d_device.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 29 matching lines @@
     return false;
   }
 
   if (feature_level < D3D_FEATURE_LEVEL_11_0) {
     LOG(LS_WARNING) << "D3D11CreateDevice returns an instance without DirectX "
                        "11 support, level "
                     << feature_level;
     return false;
   }
 
-  error = _com_error(d3d_device_.As(&dxgi_device_));
+  error = d3d_device_.As(&dxgi_device_);
   if (error.Error() != S_OK || !dxgi_device_) {
     LOG(LS_WARNING) << "ID3D11Device is not an implementation of IDXGIDevice, "
                        "this usually means the system does not support DirectX "
                        "11";
     return false;
   }
 
   return true;
 }
 
 // static
 std::vector<D3dDevice> D3dDevice::EnumDevices() {
   ComPtr<IDXGIFactory1> factory;
-  _com_error error = _com_error(
-      CreateDXGIFactory1(__uuidof(IDXGIFactory1),
-                         reinterpret_cast<void**>(factory.GetAddressOf())));
+  _com_error error = CreateDXGIFactory1(__uuidof(IDXGIFactory1),
+      reinterpret_cast<void**>(factory.GetAddressOf()));
   if (error.Error() != S_OK || !factory) {
     return std::vector<D3dDevice>();
   }
 
   std::vector<D3dDevice> result;
   for (int i = 0;; i++) {
     ComPtr<IDXGIAdapter> adapter;
-    error = _com_error(factory->EnumAdapters(i, adapter.GetAddressOf()));
+    error = factory->EnumAdapters(i, adapter.GetAddressOf());
     if (error.Error() == S_OK) {
       D3dDevice device;
       if (!device.Initialize(adapter)) {
         return std::vector<D3dDevice>();
       }
       result.push_back(std::move(device));
     } else if (error.Error() == DXGI_ERROR_NOT_FOUND) {
       break;
     } else {
       LOG(LS_WARNING) << "IDXGIFactory1::EnumAdapters returns an unexpected "
                          "error "
                       << error.ErrorMessage() << " with code " << error.Error();
       return std::vector<D3dDevice>();
     }
   }
   return result;
 }
 
 }  // namespace webrtc