i) Send ack for wake_up sensors on the socket connection instead of using Binder RPC.
ii) Cache events per connection in case there are write failures. Compute cache size
from FIFO counts of sensors.
iii) Send FlushCompleteEvent only for apps that explicitly called flush().
Change-Id: I018969736b7794b1b930529586f2294a03ee8667
56ae42613c