GuidedStepFragment: slide from both side for UI_STYLE_ENTRANCE

Simply check if the center of view in left to center of sceneRoot,
then slide to the left, otherwise slide to the right.
The position needs to be saved in captured transition values.

b/21504593

Change-Id: I310b5c998a4f763c926f67086ca065b30d2a52ba
4 files changed