Simplify input target handling in the dispatcher.

Since we no longer stream events to the application, we don't need to
keep the current list of input targets around longer than it takes
to begin the dispatch cycle.

This is part of a series of changes to improve input system pipelining.

Bug: 5963420

Change-Id: I5824b04e564c8a4dec991598292441e46c331905
2 files changed