Dispatch TaskOrg events before finishing surface placement

This ensures that calls to ITaskOrganizer.onTaskInfoChanged
are sent before an IWindowContainterTransactionCallback is
called back.

Bug: 178535312
Test: verified dispatching of task info changes happens before
onTransactionReady is called back
Test: exit PIP animation uses updated source rect hint in its
animation

Change-Id: Icb864176ce354be0d880b91b7115c7cea6f50810