zijiehe 88ac827877 Add DesktopCapturerId and attach it to DesktopFrame
This change adds a DesktopCapturerId namespace, and attaches an int to each
DesktopFrame. ScreenCapturerWinGdi and ScreenCapturerWinDirectx now actively set
this field to differentiate themselves.

BUG=679523, 650926

Review-Url: https://codereview.webrtc.org/2759493002
Cr-Original-Commit-Position: refs/heads/master@{#17329}
Committed: 41e3d9ff3b
Review-Url: https://codereview.webrtc.org/2759493002
Cr-Commit-Position: refs/heads/master@{#17347}
2017-03-22 18:38:46 +00:00
..