Sending the notification from the InputConnection layer reduces the
number of events that are handled (merged) by ContentCapture. We are
also able to handle composing span being removed; at the TextView layer,
we cannot do that as we don't know if the composing span will be added
back, which happens on typing).
Bug: 184311217
Test: manual - append chars, delete chars, replace text, move cursor to
composing text, move cursor to remove composing span, drag cursor
Test: atest android.contentcaptureservice.cts.LoginActivityTest
Change-Id: I0e9d153cf7ba2734f38cb1b6044eb7b670fb34ad
fb12492de7