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..ed1743858217c3f6e42036b297fa6b45d72a7ed8 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.
+namespace DesktopCapturerId {
+  constexpr uint32_t kUnknown = 0;
+  constexpr uint32_t kScreenCapturerWinGdi = FOURCC('W', 'S', 'G', ' ');
+  constexpr uint32_t kScreenCapturerWinDirectx = FOURCC('W', 'S', 'D', ' ');
+}  // namespace DesktopCapturerId
+
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_DESKTOP_CAPTURE_DESKTOP_CAPTURE_TYPES_H_