base/threading: fix a potential race issue on start_event_
WaitableEvent is thread-safe, but scoped_ptr<WaitableEvent> is not.
It should need a mutex lock to access the internal pointer if the
pointer may be set or reset after the thread creation that will share
the scoped_ptr.
Avoid the issue, use WaitableEvent instead of scoped_ptr<WaitableEvent>.
Review URL: https://codereview.chromium.org/1256903005
Cr-Commit-Position: refs/heads/master@{#342082}
CrOS-Libchrome-Original-Commit: 53818d55bbb632e703158aa831a03794bffd23f2
3 files changed