WebUI: Fix middle click link issue in click handler
WebUI: Fix middle click link issue in click handler

This makes sure we do not open a link twice (once due to the handler and once
due to the browser behavior).

BUG=Evan?
TEST=Evan?

Review URL: http://codereview.chromium.org/6250207

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@75149 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser