Ensure View#onInputConnectionClosedInternal() timing

This is a follow up CL to our previous CLs [1][2], which introduced
an @hide callback

  View#onInputConnectionClosedInternal()

to notify View when an is closed.

What this CL aims to do is to fix a potential problem in a code path
that has not been yet used.  Thus there should be, in theory, no
observable app compat impact.

The problem is that

  RemoteInputConnectionImpl#deactivate()

can dispatch

  A: View#onInputConnectionClosedInternal()

before

  B: InputConnection#closeConnection()

is completed when A and B need to be dispatched to two different
threads.  This can, in theory, happen when

  A: View#onInputConnectionClosedInternal()
  C: InputConnection#getHandler()

are both explicitly overridden.  That said, A is still @hide and only
by TextView, which basically does not support InputConnection with a
custom InputConnection#getHandler().

Anyway, with this CL A is guaranteed to happen after B under any
circumstances.

 [1]: Iaafb0a03126c9292c24415f866dbdd72cadfa239
      7b384751
 [2]: I9280604e7ec7e8d08c1179e6bbf0068647a41040
      7b384751

Bug: 163400105
Test: atest FrameworksCoreTests:ViewInputConnectionTest
Change-Id: I8a0e321ecf6e0b3be4b6ab1a35e6ac7259826c2e