Do not make ActivityContainer available to apps. DO NOT MERGE

A security leak was discovered whereby a malicious app could get the
IActivityContainer object from one app and use it to inject events
into another app. This fix removes the availability of the
IActivityContainer and replaces its one use with a method for
returning the information the IActivityContainer was used for.

Fixes bug 19394591.

Change-Id: Ib3cec25b25130cd8e098892c057742cfd575cfdd