Use std::unique_ptr<> to pass frame ownership in DesktopCapturer impls.

webrtc/modules/desktop_capture/win/screen_capturer_win_gdi.h

 /*
  *  Copyright (c) 2014 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 38 matching lines @@
   // Make sure that the device contexts match the screen configuration.
   void PrepareCaptureResources();
 
   // Captures the current screen contents into the current buffer. Returns true
   // if succeeded.
   bool CaptureImage();
 
   // Capture the current cursor shape.
   void CaptureCursor();
 
-  Callback* callback_;
+  Callback* callback_ = nullptr;
   std::unique_ptr<SharedMemoryFactory> shared_memory_factory_;
-  ScreenId current_screen_id_;
+  ScreenId current_screen_id_ = kFullDesktopScreenId;
   std::wstring current_device_key_;
 
   // A thread-safe list of invalid rectangles, and the size of the most
   // recently captured screen.
   ScreenCapturerHelper helper_;
 
   ScopedThreadDesktop desktop_;
 
   // GDI resources used for screen capture.
-  HDC desktop_dc_;
-  HDC memory_dc_;
+  HDC desktop_dc_ = NULL;
+  HDC memory_dc_ = NULL;
 
   // Queue of the frames buffers.
   ScreenCaptureFrameQueue<SharedDesktopFrame> queue_;
 
   // Rectangle describing the bounds of the desktop device context, relative to
   // the primary display's top-left.
   DesktopRect desktop_dc_rect_;
 
   // Class to calculate the difference between two screen bitmaps.
   std::unique_ptr<Differ> differ_;
 
-  HMODULE dwmapi_library_;
-  DwmEnableCompositionFunc composition_func_;
+  HMODULE dwmapi_library_ = NULL;
+  DwmEnableCompositionFunc composition_func_ = nullptr;
 
   // Used to suppress duplicate logging of SetThreadExecutionState errors.
-  bool set_thread_execution_state_failed_;
+  bool set_thread_execution_state_failed_ = false;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(ScreenCapturerWinGdi);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_DESKTOP_CAPTURE_WIN_SCREEN_CAPTURER_WIN_GDI_H_