Implement Tap-to-Share and Tilt-to-Share (DropShare).

o Text says "Tap to Share", but tilting (the phone on top sends) also works.
o Move text to top. Remove arrows.
o First Accelerometer value takes ~700ms :(
o Only call onP2pSendComplete on success. If the send failed, we retry quietly.
  This improves perceived reliability.
o Reduce debounce from 1000ms to 750ms.

TODO
o Never do orientation change while in the animation activity
o Get rid of black transition when entering/leaivng activity
o Figure out why it takes 700ms to get first accelerometer value
o Improve launch time of animation activity (sometimes it takes 3+ seconds)
o Consider going back to a window overlay?
o Make it snappy snappy snappy

Change-Id: Idbc8e4bb744051b7b69d234a51a3ce69e23b699f
9 files changed