Several minor improvements of DirectX capturer

webrtc/modules/desktop_capture/win/dxgi_output_duplicator.h

 /*
  *  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 93 matching lines @@
   // Spreads changes from |context| to other registered Context(s) in
   // contexts_.
   void SpreadContextChange(const Context* const context);
 
   // Returns a DesktopRect in the coordinate of |texture_|->AsDesktopFrame().
   DesktopRect SourceRect(DesktopRect rect);
 
   // Returns a DesktopRect in the coordinate of |offset|.
   DesktopRect TargetRect(DesktopRect rect, DesktopVector offset);
 
-  const D3dDevice& device_;
+  const D3dDevice device_;
   const Microsoft::WRL::ComPtr<IDXGIOutput1> output_;
   const DesktopRect desktop_rect_;
   Microsoft::WRL::ComPtr<IDXGIOutputDuplication> duplication_;
   DXGI_OUTDUPL_DESC desc_;
   std::vector<uint8_t> metadata;
   std::unique_ptr<DxgiTexture> texture_;
 
   // After each AcquireNextFrame() function call, updated_region_(s) of all
   // active Context(s) need to be updated. Since they have missed the
   // change this time. And during next Duplicate() function call, their
   // updated_region_ will be merged and copied.
   std::vector<Context*> contexts_;
 
   // The last full frame of this output and its offset. If on AcquireNextFrame()
   // failed because of timeout, i.e. no update, we can copy content from
   // |last_frame_|.
   std::unique_ptr<SharedDesktopFrame> last_frame_;
   DesktopVector last_frame_offset_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_DESKTOP_CAPTURE_WIN_DXGI_OUTPUT_DUPLICATOR_H_