Fixed misplacement of cancel(X) button for Face Unlock

Before the FUL service started, the FUL cancel button was positioned
off of the right side of the window.  This was because the
FaceUnlockView (derived from RelativeLayout) was calling
super.onMeasure() incorrectly, preventing it from using the new
'square' size when laying out child views.

Change-Id: I2f1e86617da5c8f37123febab2e433288bdea062