OnionSoup: Remove all uses of Blink's WaitableEvent in WorkerSchedulerProxyTest

This CL replaces all uses of Blink's WaitableEvent with base::WaitableEvent
in worker_scheduler_proxy_unittests.cc. To remove all uses of it, this CL needs
change the type of |throtting_state_changed| from a reference to std::unique_ptr
in order to apply the initial arguments, because Blink's WaitableEvent has used
a different initial argument.

Bug: 919388
Change-Id: I0f24c94f0a59a04e691f02a5a7ac7d0c2595ac7d
Reviewed-on: https://chromium-review.googlesource.com/c/1481282
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Gyuyoung Kim <gyuyoung@igalia.com>
Cr-Commit-Position: refs/heads/master@{#634470}
1 file changed