base

Add ability to promote fields.

This adds the ability to promote private fields to public ones to
enable layoutlib to access them. This was first added in change
b556decf75b2b084e1aed54ac7fa23a141eedb7f, but reverted in
847b0d3ad22a47e0bca3d8bc8168fea7a0ba2f80. This is essentially a revert
of the change again, but without the SimpleMonthView related stuff.

Also, promote the Choreographer's field as is needed to support
animations.

Change-Id: Iee45a465c7a1cadd362c1841385941e6232e4900