Add CHECK to diagnose the crash seen only on lucas with software mirroring.

BUG=309808

Review URL: https://codereview.chromium.org/113083003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240457 0039d316-1c4b-4281-b951-d872f2087c98
Preloads the Effects plugin through the Hangout Services extension.
It's triggered 2 minutes after Chrome startup.

BUG=

Review URL: https://codereview.chromium.org/113113002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240458 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240458