Make sure that ApmHelpersTest tests don't enter a tight loop.

BUG=webrtc:7219, webrtc:7290
TBR=solenberg@webrtc.org

Review-Url: https://codereview.webrtc.org/2729133002
Cr-Original-Commit-Position: refs/heads/master@{#16996}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: f0d7b2b5077fd3fb655ea76b8b6e3c4b8ab8afef
1 file changed