Fix IOOBE due to internal list being updated from remove

This CL removes all prepareChildren(), leaving
only the one in onMeasure(). This makes the state
more stable since we will only update it within a
layout pass. This also reduces any unnecessary work.

BUG: 30252077
Change-Id: Ibd00a3c3ede1dd654b0ed6d1d8d8d1c8da94e57a
2 files changed