EditText: Proper support for "textIsSelectable".

All I've done is change the order in which the textview's attributes
are being checked. Not sure if this breaks anything but nothing jumps
out as something that can break from a brief inspection of the code.
I'll revert this changelist if something breaks as a result of this.

Bug: 30874589
Change-Id: I0e2411eab6e952a0d10eedd8c2d3d073ea436f56