Introduced in I740600d18859422b2f98a5ef92d0321f6e9615a2.
We need to prevent the default action (navigating a link) so that
our custom code has a chance to run. Before it was synchronous so
it called location.href before default action had a chance to execute.
When it was made asynchronous, the default action got executed before
our custom code.
Change-Id: I292f99aa5f5ff536d8197174c317018462685866