FIx handleLinkClick to handle sub-elements within links

If the user clicks on an element descendant of the link, it will
bubble up, and hit the delegated listener on the <a> element.  However,
'target' will be set to what they actually clicked on.

This means accessing the href will generally yield undefined if they
don't click on the link.

However, currentTarget is always whatever element it has bubbled up to,
in this case the actual <a> element.

Bug: 71494
Change-Id: I317989871bddd3cc178bcc012988b1d66520dcba
(cherry picked from commit f2a813bbbe223cf1ff83655370a24ef2db136aa8)
Merge "FIx handleLinkClick to handle sub-elements within links" into wmf/1.25wmf1