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

webrtc/modules/desktop_capture/window_capturer_unittest.cc

Index: webrtc/modules/desktop_capture/window_capturer_unittest.cc
diff --git a/webrtc/modules/desktop_capture/window_capturer_unittest.cc b/webrtc/modules/desktop_capture/window_capturer_unittest.cc
index 32b8b8f23cbba1a24910f85b274102d42a183a79..d2d326e39f4b0e3cee5a64488bb668fb3f4d6db2 100644
--- a/webrtc/modules/desktop_capture/window_capturer_unittest.cc
+++ b/webrtc/modules/desktop_capture/window_capturer_unittest.cc
@@ -31,7 +31,10 @@ class WindowCapturerTest : public testing::Test,
   void TearDown() override {}
 
   // DesktopCapturer::Callback interface
-  void OnCaptureCompleted(DesktopFrame* frame) override { frame_.reset(frame); }
+  void OnCaptureResult(DesktopCapturer::Result result,
+                       std::unique_ptr<DesktopFrame> frame) override {
+    frame_ = std::move(frame);
+  }
 
  protected:
   std::unique_ptr<WindowCapturer> capturer_;