Several minor improvements of DirectX capturer

webrtc/modules/desktop_capture/win/dxgi_texture_staging.cc

Index: webrtc/modules/desktop_capture/win/dxgi_texture_staging.cc
diff --git a/webrtc/modules/desktop_capture/win/dxgi_texture_staging.cc b/webrtc/modules/desktop_capture/win/dxgi_texture_staging.cc
index 7478728143d0d8f93c274709e5d9207fc67073d4..23dff5a948fe81627a9bb3922bee55b221c67876 100644
--- a/webrtc/modules/desktop_capture/win/dxgi_texture_staging.cc
+++ b/webrtc/modules/desktop_capture/win/dxgi_texture_staging.cc
@@ -38,9 +38,13 @@ bool DxgiTextureStaging::InitializeStage(ID3D11Texture2D* texture) {
     return false;
   }
 
+  desc.ArraySize = 1;
   desc.BindFlags = 0;
   desc.CPUAccessFlags = D3D11_CPU_ACCESS_READ;
+  desc.MipLevels = 1;
   desc.MiscFlags = 0;
+  desc.SampleDesc.Count = 1;
+  desc.SampleDesc.Quality = 0;
   desc.Usage = D3D11_USAGE_STAGING;
   if (stage_) {
     AssertStageAndSurfaceAreSameObject();
@@ -58,8 +62,8 @@ bool DxgiTextureStaging::InitializeStage(ID3D11Texture2D* texture) {
     RTC_DCHECK(!surface_);
   }
 
-  _com_error error = _com_error(device_.d3d_device()->CreateTexture2D(
-      &desc, nullptr, stage_.GetAddressOf()));
+  _com_error error = device_.d3d_device()->CreateTexture2D(

[Sergey Ulanov, 2016/09/19 22:15:19]

do you need _com_error here instead of HRESULT?
Same question about other places where _com_error is used to store HRESULT.

[Hzj_jie, 2016/09/19 23:15:27]

What _com_error can provide is the functionality to convert a non-user-friendly
magic Windows error number into a meaningful string by calling its
ErrorMessage() function.
The ErrorMessage() has been used widely in the log output.

+      &desc, nullptr, stage_.GetAddressOf());
   if (error.Error() != S_OK || !stage_) {
     LOG(LS_ERROR) << "Failed to create a new ID3D11Texture2D as stage, error "
                   << error.ErrorMessage() << ", code " << error.Error();