History: Fix deletion of individual items on mobile platforms.

The fade-out transition happens differently on mobile: the entry-box is
faded out, rather than its parent. Due to this difference,
http://crrev.com/234522 caused a regression in deletions on mobile.

The fix is to stop propagation when an event is handled, rather than
ignoring the event if currentTarget != target.

R=sergiu@chromium.org
BUG=323148

Review URL: https://codereview.chromium.org/113343004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241283 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241283