When a new focus owner lands on the stack, don't just make the
previous top of the stack lose focus, propagate the loss throughout
the stack.
Only dispatch focus loss on focus loss state change
Remove canDispatchFocus() method as it now doesn't need to be known
(and shouldn't be known) outside of the implementation.
Fix error where the focus code for a focus gain request should
always be a focus loss code.
Bug 8315302
Change-Id: I92c8f51fdcc090851d34d00fefed916e25da40c1
cbb212ff6f