Remove references of MessageLoopForIO in /chrome/renderer/media/cast_ipc_dispatcher_unittest.cc

MessageLoopForIO will go away soon use ScopedTaskEnvironment instead.

ScopedTaskEnvironment will per default start a ThreadPool, which should
be fine in most of the cases. If you believe your test needs to make sure
that no ThreadPool runs let me know and I will update the patch.

BUG=891670
This CL was uploaded by git cl split.

R=miu@chromium.org

Change-Id: I692e8ce91f43e17c5d0ad58dc1b194145490a4d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1733613
Commit-Queue: Carlos Caballero <carlscab@google.com>
Auto-Submit: Carlos Caballero <carlscab@google.com>
Reviewed-by: Yuri Wiitala <miu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683976}
1 file changed