Reduce EntropyMixer seed size from 4096 to 512 bytes.

The suggested seed size from Linux drivers/char/random.c is 512 bytes
rather than the 4096 bytes currently used.

Change-Id: I3dd55105f0a95ce9cda34b4cf08987b8a28c4ac9
Privatize PhoneWindowManager

on my gen2 N7 this lowered system memory usage by 50-100 mb

PS2: move hardware key stuff to it's own observer

Change-Id: I9872c32c695abad56cd07f50893fa7eda645c5b2
Merge changes I9872c32c,I3dd55105 into jb43

* changes:
  Privatize PhoneWindowManager
  Reduce EntropyMixer seed size from 4096 to 512 bytes.