Convert the DCHECK to CHECK for bad NOTIFICATION_EXTENSION_VIEW_REGISTERED message.

BUG=294687
TBR=yoshiki@chromium.org

Review URL: https://codereview.chromium.org/109653017

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242254 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242254