Revert of Add CastMediaBlocker and BrowserTest (patchset #5 id:80001 of https://codereview.chromium.org/2330243002/ )

Reason for revert:
Test is failing on Cast Linux:
https://build.chromium.org/p/chromium.linux/builders/Cast%20Linux/builds/31563

Original issue's description:
> Add CastMediaBlocker and BrowserTest
>
> CastMediaBlocker is a class which can prevent media from being played
> on a web page.
>
> BUG=NONE
> TEST=ChromecastShellMediaBlockingBrowserTest
>
> Committed: https://crrev.com/502bcc946bd12e907572f8b22ef4a0abbc8190d0
> Cr-Commit-Position: refs/heads/master@{#418897}

TBR=halliwell@chromium.org,byungchul@chromium.org,derekjchow@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=NONE

Review-Url: https://codereview.chromium.org/2345053002
Cr-Commit-Position: refs/heads/master@{#418950}
6 files changed