Add UMA_HISTOGRAM_ENUMERATION PrintPreview.PreviewEvent.

NOTRY=true

Review URL: https://codereview.chromium.org/25535007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226706 0039d316-1c4b-4281-b951-d872f2087c98
Blink roll 158766:158774

http://build.chromium.org/f/chromium/perf/dashboard/ui/changelog_blink.html?url=/trunk&range=158767:158774&mode=html
TBR=
BUG=

Review URL: https://codereview.chromium.org/25823003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226707 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226706
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226708 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226707
SVN changes up to revision 226708