This logically relands the CL [1], which added an @hide method
CursorAnchorInfo#createForAdditionalParentMatrix().
The corresponding change was once removed in [2].
This is a preparation to reland a change that supports
InputMethodManager#reportActivityView() again.
[1] Ic7f9057623ffc61ec7a6121735dc39adecf4649d
[2] I0a05453eeed863db5bfe4b965ab4bcbad67f2783
Bug: 224424149
Test: CursorAnchorInfoTest
Change-Id: I0a411453c7c26795d28e913a96be8eb8fa3684d7