Fix issue #6048808: sometimes auto-correct is inactive

My previous change to speed up the time the IME is dismissed was
fundamentally flawed.  That change basically switched the order
the application called the input method manager service from doing
startInput() and then windowGainedFocus(), to first windowGainedFocus()
and then startInput().

The problem is that the service relies on startInput() being done
first, since this is the mechanism to set up the new input focus,
and windowGainedFocus() is just updating the IME visibility state
after that is done.  However, by doing the startInput() first, that
means in the case where we are going to hide the IME we must first
wait for the IME to re-initialize editing on whatever input has
focus in the new window.

To address this, the change here tries to find a half-way point
between the two.  We now do startInput() after windowGainedFocus()
only when this will result in the window being hidden.

It is not as easy as that, though, because these are calls on to
the system service from the application.  So being able to do that
meant a fair amount of re-arranging of this part of the protocol
with the service.  Now windowGainedFocus() is called with all of
the information also needed for startInput(), and takes care of
performing both operations.  The client-side code is correspondingly
rearranged so that the guts of it where startInput() is called can
instead call the windowGainedFocus() entry if appropriate.

So...  in theory this is safer than the previous change, since it
should not be impacting the behavior as much.  In practice, however,
we are touching and re-arranging a lot more code, and "should" is
not a promise.

Change-Id: Icb58bef75ef4bf9979f3e2ba88cea20db2e2c3fb