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

webrtc/modules/desktop_capture/screen_capturer_mock_objects.h

Index: webrtc/modules/desktop_capture/screen_capturer_mock_objects.h
diff --git a/webrtc/modules/desktop_capture/screen_capturer_mock_objects.h b/webrtc/modules/desktop_capture/screen_capturer_mock_objects.h
index 7264249e0fb0c70403ece92b121b5b54e7678c13..800da95f101c4bdf66d079156cac0e46ac1eef80 100644
--- a/webrtc/modules/desktop_capture/screen_capturer_mock_objects.h
+++ b/webrtc/modules/desktop_capture/screen_capturer_mock_objects.h
@@ -36,7 +36,11 @@ class MockScreenCapturerCallback : public ScreenCapturer::Callback {
   MockScreenCapturerCallback() {}
   virtual ~MockScreenCapturerCallback() {}
 
-  MOCK_METHOD1(OnCaptureCompleted, void(DesktopFrame*));
+  MOCK_METHOD1(OnCaptureCompletedPtr,
+               void(std::unique_ptr<DesktopFrame>* frame));

[Wez, 2016/05/18 01:29:50]

In our other tests we un-wrap the |frame| so that this would be DesktopFrame* -
what's the rationale for passing unique_ptr<>* instead?

[Sergey Ulanov, 2016/05/31 12:02:48]

When passing unique_ptr<>* the test doesn't have to delete the frame if it
doesn't need it, which makes the tests simpler. 

[Wez, 2016/06/01 21:29:04]

Ah, very nice. Sounds like we should follow this pattern in new tests in place
of the old bare-pointer approach.

+  void OnCaptureCompleted(std::unique_ptr<DesktopFrame> frame) override {
+    OnCaptureCompletedPtr(&frame);
+  }
 
  private:
   RTC_DISALLOW_COPY_AND_ASSIGN(MockScreenCapturerCallback);