[RunLoop] Ban off-thread usage of Quit*Closure()

The only reason for the fancy detach in RunLoop::RunWithTimeout() was to
enable calls to Quit*Closure() from another thread while running. But
that's not necessary as Quit*() is thread-safe (fixed the callers that
did so).

Bug: 715235, 961608
Change-Id: I3f8dca467a6ff97c87022f7c0c57ab8d4bc8df1d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1663382
Commit-Queue: Gabriel Charette <gab@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Reviewed-by: Gary Kacmarcik <garykac@chromium.org>
Reviewed-by: Tim Schumann <tschumann@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: Bo <boliu@chromium.org>
Reviewed-by: Wei Li <weili@chromium.org>
Reviewed-by: Eric Orth <ericorth@chromium.org>
Reviewed-by: Joshua Bell <jsbell@chromium.org>
Reviewed-by: Joe Downing <joedow@chromium.org>
Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Reviewed-by: Chris Hamilton <chrisha@chromium.org>
Reviewed-by: Eric Roman <eroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672794}
16 files changed