Allow a GLSurfaceView to be reattached to a window.

This approach is more backwards-compatible than the previous attempt.

The onDetachedFromWindow case is unchanged from the "classic"
GLSurfaceView behavior, except that we don't throw a NPE if the
renderer has never been set.

Change-Id: Ia8103a73366ddb13be44f16b789c929e75ddc792