Cleaned-up logic for determining clip rect for transitions animations.

Previous logic led to several edge cases which fixes sometimes broke
other edge cases. New logic uses the clip rect provided by the
transformation as-is and doesn't try to adjust it based on window
flags. Correct clip rect is set in
WindowManagerService#applyAnimationLock using the content insets
before the animation is loaded.

Bug: 21727851
Bug: 20652683
Bug: 19523205
Bug: 15046646
https://code.google.com/p/android/issues/detail?id=161362
Change-Id: I2d4ed6196edb8ee8c401fe9a242aec70d3494574