FakeVideoCapturerWithTaskQueue overrides frame related methods
and delivers frame callbacks on a TaskQueue (separate thread),
as is (must be) expected by the implementations being tested.
I'm also moving the implementation out of the header and into
a separate source file.
In this CL, I'm updating one test to use the new class but
more will follow.
Bug: webrtc:8848
Change-Id: I5403c6bcc8b757e9d7fa9c368506667707b37b28
Reviewed-on: https://webrtc-review.googlesource.com/48360
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Commit-Queue: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21948}
1829af6a39