Revert "Measure whether muted videos that started playing with play() become visible at some point"

This reverts commit 9d961d0a083fe4ebd8c200c31b87d75e4727958b.

Seems to be leaking, broke WebKit Leak bots here:
https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Leak/builds/20963

BUG=627539,622720

TBR=zqzhang@chromium.org
NOTRY=true
NOPRESUBMIT=true
NOTREECHECKS=true

Review-Url: https://codereview.chromium.org/2141093003
Cr-Commit-Position: refs/heads/master@{#404836}
8 files changed