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

webrtc/modules/desktop_capture/cropping_window_capturer.cc

 /*
  *  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 56 matching lines @@
     selected_window_ = id;
     return true;
   }
   return false;
 }
 
 bool CroppingWindowCapturer::BringSelectedWindowToFront() {
   return window_capturer_->BringSelectedWindowToFront();
 }
 
-void CroppingWindowCapturer::OnCaptureCompleted(DesktopFrame* frame) {
-  std::unique_ptr<DesktopFrame> screen_frame(frame);
-
+void CroppingWindowCapturer::OnCaptureCompleted(
+    std::unique_ptr<DesktopFrame> screen_frame) {
   if (!ShouldUseScreenCapturer()) {
     LOG(LS_INFO) << "Window no longer on top when ScreenCapturer finishes";
     window_capturer_->Capture(DesktopRegion());
     return;
   }
 
-  if (!frame) {
+  if (!screen_frame) {
     LOG(LS_WARNING) << "ScreenCapturer failed to capture a frame";
-    callback_->OnCaptureCompleted(NULL);
+    callback_->OnCaptureCompleted(std::unique_ptr<DesktopFrame>());
     return;
   }
 
   DesktopRect window_rect = GetWindowRectInVirtualScreen();
   if (window_rect.is_empty()) {
     LOG(LS_WARNING) << "Window rect is empty";
-    callback_->OnCaptureCompleted(NULL);
+    callback_->OnCaptureCompleted(std::unique_ptr<DesktopFrame>());
     return;
   }
 
-  std::unique_ptr<DesktopFrame> window_frame(
-      CreateCroppedDesktopFrame(screen_frame.release(), window_rect));
-  callback_->OnCaptureCompleted(window_frame.release());
+  callback_->OnCaptureCompleted(
+      CreateCroppedDesktopFrame(std::move(screen_frame), window_rect));
 }
 
 #if !defined(WEBRTC_WIN)
 // static
 WindowCapturer*
 CroppingWindowCapturer::Create(const DesktopCaptureOptions& options) {
   return WindowCapturer::Create(options);
 }
 #endif
 
 }  // namespace webrtc