Move content/renderer/media_recorder/video_track_* to blink

This is a part of moving media recorder implementation to blink.
This CL moves content/renderer/media_recorder/video_track_* files
to blink, adds methods and replaces some implementation with
blink variant.
- Add CopyVideoFrame in WebGraphicsContext3DProvider
- Add media::GpuVideoAcceleratorFactories in Platform
- std::vector, base::flat_map -> blink::Vector, WTF::HashMap
- base::Thread -> blink::Thread
- main_render_thread_checker_ -> IsMainThread()
- base::BindOnce, base::Bind -> WTF::Bind, WTF::BindRepeating
- Remove base::test::ScopedTaskEnvironment
- Replace ThreadTaskRunnerHandle with Platform::Current()->GetIOTaskRunner()

Bug: 960665
Change-Id: I8d82f850b9c39ce9d4b892ea24a075ce1e6288f5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1646810
Commit-Queue: Miyoung Shin <[email protected]>
Reviewed-by: Guido Urdaneta <[email protected]>
Reviewed-by: Antonio Gomes <[email protected]>
Reviewed-by: Kentaro Hara <[email protected]>
Cr-Commit-Position: refs/heads/master@{#670371}
33 files changed