Add DesktopFrame rotation functions

webrtc/modules/desktop_capture/desktop_frame.h

Index: webrtc/modules/desktop_capture/desktop_frame.h
diff --git a/webrtc/modules/desktop_capture/desktop_frame.h b/webrtc/modules/desktop_capture/desktop_frame.h
index d491135029fe45f79940e81d1c042961ef0ab7cf..1d4df0e40492a343dec1832336f488948c80144c 100644
--- a/webrtc/modules/desktop_capture/desktop_frame.h
+++ b/webrtc/modules/desktop_capture/desktop_frame.h
@@ -16,6 +16,7 @@
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/modules/desktop_capture/desktop_geometry.h"
 #include "webrtc/modules/desktop_capture/desktop_region.h"
+#include "webrtc/modules/desktop_capture/rgba_color.h"
 #include "webrtc/modules/desktop_capture/shared_memory.h"
 #include "webrtc/typedefs.h"
 
@@ -26,6 +27,9 @@ class DesktopFrame {
  public:
   // DesktopFrame objects always hold RGBA data.
   static const int kBytesPerPixel = 4;
+  static_assert(kBytesPerPixel == sizeof(RgbaColor),
+                "A pixel in DesktopFrame should be safe to be represented by a "
+                "RgbaColor");
 
   virtual ~DesktopFrame();
 
@@ -68,6 +72,18 @@ class DesktopFrame {
   // A helper to return the data pointer of a frame at the specified position.
   uint8_t* GetFrameDataAtPos(const DesktopVector& pos) const;
 
+  // Whether current instance equals to the |other| in both size() and data().
+  bool DataEquals(const DesktopFrame& other) const;
+
+  // Paints the pixel at |pos| with |color|. This should be for test purpose
+  // only. This function triggers check failure if pos is out of current
+  // DesktopFrame.
+  void Paint(DesktopVector pos, RgbaColor color);

[Sergey Ulanov, 2016/11/15 02:28:10]

Do we really need this function here? RgbaColor is currently marked as
tests-only (see the comments in the header) and I'd prefer to keep it restricted
to tests. If you use this function only in tests then maybe add make it a static
function in a separate test_utils file. Same applies for DataEquals() and
Clear().

[Hzj_jie, 2016/11/15 05:17:02]

Sure. Updated.

+
+  // Clears DesktopFrame by set entire data() buffer into 0. This should be for
+  // test purpose only.
+  void Clear();
+
  protected:
   DesktopFrame(DesktopSize size,
                int stride,