Add DesktopCapturerId and attach it to DesktopFrame

webrtc/modules/desktop_capture/desktop_capture_types.h

Index: webrtc/modules/desktop_capture/desktop_capture_types.h
diff --git a/webrtc/modules/desktop_capture/desktop_capture_types.h b/webrtc/modules/desktop_capture/desktop_capture_types.h
index 9a6162a766d5e7da2ce7db918dab0923a0a425f1..eac2468bb7ab31fc6637ff2e1dbbbdd32be5a58e 100644
--- a/webrtc/modules/desktop_capture/desktop_capture_types.h
+++ b/webrtc/modules/desktop_capture/desktop_capture_types.h
@@ -13,6 +13,7 @@
 
 #include <stdint.h>
 
+#include "webrtc/media/base/videocommon.h"
 #include "webrtc/typedefs.h"
 
 namespace webrtc {
@@ -36,6 +37,14 @@ const ScreenId kFullDesktopScreenId = -1;
 
 const ScreenId kInvalidScreenId = -2;
 
+// An integer to attach to each DesktopFrame to differentiate the generator of
+// the frame.
+enum class DesktopCapturerId {

[Sergey Ulanov, 2017/03/21 00:39:36]

I think this shouldn't be a class enum as we want the set of capturers to be
extensible, so the capturer ID should be 32-bit integer, without restricting to
an enum value.

[Hzj_jie, 2017/03/21 18:40:39]

Done.

+  UNKNOWN = FOURCC(0, 0, 0, 0),

[Sergey Ulanov, 2017/03/21 00:35:43]

UNKNOWN = 0

[Hzj_jie, 2017/03/21 18:40:39]

Done.

+  SCREEN_CAPTURER_WIN_GDI = FOURCC('W', 'S', 'G', 0),
+  SCREEN_CAPTURER_WIN_DIRECTX = FOURCC('W', 'S', 'D', 0),

[Sergey Ulanov, 2017/03/21 00:35:43]

' ' instead of 0 please.
Also would be easier to understand these names if they were "GDI " and "DXGI"?

[Hzj_jie, 2017/03/21 18:40:39]

I am trying to make each bit useful, here WSG means Windows Screencapturer Gdi,
and the forth bit is preserved (changed to ' ').

[Sergey Ulanov, 2017/03/21 18:54:37]

I got that, but "GDI" would be much clearer if one sees it logs and it's just as
unambiguous (we don't have GDI capturer on Linux or Mac). For window capturer on
windows we could use GDIW.

[Hzj_jie, 2017/03/21 19:38:49]

Done.

+};
+
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_DESKTOP_CAPTURE_DESKTOP_CAPTURE_TYPES_H_