Rename main_thread_scheduler.{h,cc} to main_thread_scheduler_impl.

These files were renamed in crrev.com/c/986112, but they should have
"_impl" in the back. This patch corrects those names.

Bug: 826203
Change-Id: Ib4cf5e51f1e5cd8d517486a0e1fb177bb30d8f78
Reviewed-on: https://chromium-review.googlesource.com/994504
Commit-Queue: Yuta Kitamura <yutak@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549436}
26 files changed