[WebRTC] A real ScreenCapturer test

webrtc/modules/desktop_capture/desktop_frame.cc

Index: webrtc/modules/desktop_capture/desktop_frame.cc
diff --git a/webrtc/modules/desktop_capture/desktop_frame.cc b/webrtc/modules/desktop_capture/desktop_frame.cc
index 51cf568aa0b6a35c3be1f3901df90532a2d8ea3b..b3590cb1d84cc8033906ce0ab1af8440c4c38b61 100644
--- a/webrtc/modules/desktop_capture/desktop_frame.cc
+++ b/webrtc/modules/desktop_capture/desktop_frame.cc
@@ -57,6 +57,11 @@ uint8_t* DesktopFrame::GetFrameDataAtPos(const DesktopVector& pos) const {
   return data() + stride() * pos.y() + DesktopFrame::kBytesPerPixel * pos.x();
 }
 
+DesktopVector DesktopFrame::GetPosAtFrameData(const uint8_t* const pos) const {
+  return DesktopVector((pos - data()) % stride() / DesktopFrame::kBytesPerPixel,
+                       (pos - data()) / stride());
+}
+
 BasicDesktopFrame::BasicDesktopFrame(DesktopSize size)
     : DesktopFrame(size, kBytesPerPixel * size.width(),
                    new uint8_t[kBytesPerPixel * size.width() * size.height()],