GitLab

linux: Add support for undo in the omnibox.

GtkTextView does not support undo. So borrow the relevant code from
GtkSourceView.

BUG=18210
TEST=None

Patch from sadrul <sadrul@chromium.org>

Review URL: http://codereview.chromium.org/3429025

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@60744 0039d316-1c4b-4281-b951-d872f2087c98