Fix PiP animation errors introduced in crop refactoring.

Firstly, pinned stack now uses final crop only, so we need to scale
to the width/height computed there, not as computed for the crop.
Furthermore mTmpClipRect is no longer used directly to set the crop,
so clearing it in the pinned animation code had no effect. This fixes
the worst of the visual errors so people stop filing bugs while I
rework this logic entirely.

Bug: 34823229
Bug: 32881014
Bug: 33245930
Test: Manual with PiP activities on Fugu.
Change-Id: I45d2def5138f3cc278408a9209b5e5c40cece80b