To make desktopCapture autotest in chromium more meaningful, it's better
to creake fake capturer of each capture type. Here we can reuse the
FakeDesktopCapturer for window capture in chromium.
Bug: chromium:699201
Change-Id: Icbe134d99cbd4980bf27fe74c1c629a1469836ea
Reviewed-on: https://webrtc-review.googlesource.com/26360
Reviewed-by: Zijie He <zijiehe@chromium.org>
Commit-Queue: Brave Yao <braveyao@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20901}
99206df620