Add MAY_BLOCK ScopedBlockingCall in WaitableEvent::*Wait*.

Care has been taken to avoid changing worker capacity when the
TaskScheduler code itself waits on a WaitableEvent.

Bug: 738104
Change-Id: If0c7220c6a5602ba2969fbc867e4bc7b81469137
Reviewed-on: https://chromium-review.googlesource.com/654058
Commit-Queue: Francois Doray <fdoray@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: Robert Liao <robliao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501001}

CrOS-Libchrome-Original-Commit: 3abc0c0cc1e7ae9c5629f417609ae478d98b09ab
5 files changed
tree: 65067a95cd709d8b28ef60b88485ff2edf1abbde
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/