Implement nice transitions for light status bar

- When the flag changes, apply an animation from the current value
- When the flag change is caused by an app transition, synchronize
  the status bar animation with the app transition animation.
  PhoneWindowManager calculates the timings based on some heuristics
  of the app transition animations and supplies these timings to
  StatusBarService.

Bug: 19233606
Change-Id: I4f99afba8f1eebb3524699ed4d7fbafee5463a37