[MessageLoop] Update high-res tasks comment in TriageQueue::ReloadFromIncomingQueueIfEmpty

This is part of a few precursor cleanups before moving this code to
MessageLoopTaskRunner (to split incoming task source logic from
IncomingTaskQueue and allow mocking the task source).

R=robliao@chromium.org

Bug: 708584
Change-Id: Ic35654fd4cc38a7d6cc52fe428a38b27ce108046
Reviewed-on: https://chromium-review.googlesource.com/1079248
Commit-Queue: Gabriel Charette <gab@chromium.org>
Reviewed-by: Robert Liao <robliao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563797}
1 file changed