Disappear from OWNERS for generic extensions directories.

Review URL: https://codereview.chromium.org/105523004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240817 0039d316-1c4b-4281-b951-d872f2087c98
[Most Visited] Log per-provider impressions to UMA.

Ensures every thumbnail iframe logs in UMA its position in a histogram that matches the name of the suggestion provider.

BUG=None
TEST=None

Review URL: https://codereview.chromium.org/114413003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240818 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240817
SVN changes up to revision 240818