Add extension install verification entries to histograms.xml

These histograms got renamed and reworked in
https://codereview.chromium.org/132373002 to be more useful, but the existing
ones are already in the M33 branch and we'd like to be able to see their
results. Later on we'll be able to remove these ones, and that work is tracked
by the bug referenced below.

BUG=333934
R=asvitkine@chromium.org

Review URL: https://codereview.chromium.org/136453006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245013 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245013
Revert 245012 "Add include"

> Add include
> 
> TBR=sky@chromium.org
> 
> Review URL: https://codereview.chromium.org/134173003

TBR=ben@chromium.org

Review URL: https://codereview.chromium.org/138733004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245015 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245015