Random articles.

* mhurd asked to make Random tappable in W menu (as opposed to shake).
* See PS3 for the version using shake and with W menu and Settings app backing.
* See PS7 for the version supporting lower-left corner swipe + W menu tap (but not shake).

Change-Id: I7f6948de527fa4dda2a00d157fd44adf02f7aaaa
Merge "Random articles."