Code:    void WaitForCallback() {
     if (!use_audio_thread_) {
       base::RunLoop().RunUntilIdle();
       return;
     }
    media::WaitableMessageLoopEvent event;
     audio_thread_.task_runner()->PostTaskAndReply(
         FROM_HERE, base::Bind(&base::DoNothing), event.GetClosure());
    event.RunAndWait();
    base::RunLoop().RunUntilIdle();
  }

Vulnerability Type: DoS 
CWE ID: 
Summary: Multiple unspecified vulnerabilities in Google Chrome before 43.0.2357.65 allow attackers to cause a denial of service or possibly have other impact via unknown vectors.
Commit Message: Switching AudioOutputAuthorizationHandler from using AudioManager interface to AudioSystem one.

BUG=672468
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2692203003
Cr-Commit-Position: refs/heads/master@{#450939}