Add support for injecting events into ActivityContainers. (DO NOT MERGE)

Modified ActivityView to inject touch events it receives back into
its activity container.  The container then injects the event into
the input system along with the display id of the underlying virtual
display.

Enhanced the input system to support concurrent dispatch of touch
events on multiple displays which is required for this to work.

Change-Id: I9cf1870db3be6f99a52ed9a1e3ceafe42c940093