Add migration hint for OverrideThreadForMessage().

TBR=fdoray@chromium.org

NOTRY=True

Bug: 689520
Change-Id: I3e53c759f0874e3a249d347a94a58eac761c52f4
Reviewed-on: https://chromium-review.googlesource.com/588132
Reviewed-by: Gabriel Charette <gab@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#489821}
1 file changed