Coalesce input events that arrive faster than 333Hz. (DO NOT MERGE)

Some drivers report individual finger updates one at a time
instead of all at once.  When 10 fingers are down, this can
cause the framework to have to handle 10 times as many events
each with 10 times as much data.  Applications like
PointerLocation would get significantly bogged down by all
of the redundant samples.

This change coalesces samples that are closely spaced in time,
before they are dispatched, as part of the motion event batching
protocol.

Increased the size of the InputChannel shared memory buffer so
that applications can catch up faster if they accumulate a
backlog of samples.

Change-Id: Ibc6abf8af027d9003011ac75caa12941080caba3