Add window focused state to TaskInfo.

Add a helper method Task#dispatchTaskInfoChangedIfNeeded to avoid
checking for isOrganized() every time we need to dispatch a task info
change.

Bug: 165794880
Test: Window focused state is pushed to WM shell.
Change-Id: I3e1272884f4ca9021c82b0df71ff2f7c5a6fea83