Log error messages in windows video capture

media/video/capture/win/video_capture_device_mf_win.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.
 
 #include "media/video/capture/win/video_capture_device_mf_win.h"
 
 #include <mfapi.h>
 #include <mferror.h>
 
 #include "base/memory/ref_counted.h"
@@ skipping 314 matching lines @@
       // fail with HRESULT_FROM_WINHRESULT_FROM_WIN32(ERROR_INVALID_FUNCTION).
       // It's not clear to me why this is, but it is possible that it has
       // something to do with this bug:
       // http://support.microsoft.com/kb/979567
       OnError(hr);
     }
   }
 }
 
 void VideoCaptureDeviceMFWin::OnError(HRESULT hr) {
-  std::string log_msg = base::StringPrintf("VideoCaptureDeviceMFWin: %x", hr);
-  DLOG(ERROR) << log_msg;
+  const std::string log_msg =
+      base::StringPrintf("VideoCaptureDeviceMFWin: %x", hr);
+  const std::string last_error_message =
+      logging::SystemErrorCodeToString(logging::GetLastSystemErrorCode());
+  DPLOG(ERROR) << log_msg;

[mcasas, 2014/08/26 15:38:18]

l.338 will in all probability clear the last error id,
so perhaps here you should do:
DLOG(ERROR) << log_msg << ", OS message: " << last_error_message;

Note DLOG(ERROR) != DVLOG(1) 

[magjed_chromium, 2014/08/26 17:20:28]

Done. Btw, I don't think GetLastSystemErrorCode clears the last error (from
reading the documentation, not testing).

   if (client_.get())
-    client_->OnError(log_msg);
+    client_->OnError(log_msg + " : " + last_error_message);
 }
 
 }  // namespace media