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

libs/ui/InputTransport.cpp

@@ -27,8 +27,14 @@
 
 namespace android {
 
+#define ROUND_UP(value, boundary) (((value) + (boundary) - 1) & ~((boundary) - 1))
+#define MIN_HISTORY_DEPTH 20
+
 // Must be at least sizeof(InputMessage) + sufficient space for pointer data
-static const int DEFAULT_MESSAGE_BUFFER_SIZE = 16384;
+static const int DEFAULT_MESSAGE_BUFFER_SIZE = ROUND_UP(
+        sizeof(InputMessage) + MIN_HISTORY_DEPTH
+                * (sizeof(InputMessage::SampleData) + MAX_POINTERS * sizeof(PointerCoords)),
+        4096);
 
 // Signal sent by the producer to the consumer to inform it that a new message is
 // available to be consumed in the shared memory buffer.