DO NOT MERGE: Fix FLAG_NOT_FOCUSABLE ime target

Windows with FLAG_NOT_FOCUSABLE can not be IME target unless alpha is
zero (i.e. app is using transparent window to detect IME for legacy
reasons).
Going forward we can improve this with the todo already mentioned in the
code block.

Bug: 145812508
Fix: 149899590
Test: Manually verified using steps in bug.

Change-Id: I0e7db484dd4f9b584998b9f922fd46030fb6fb72
(cherry picked from commit f3a2b52e16a6a4e91ade996a713cbb1d2b51172b)
(cherry picked from commit b17e22cd7676c0cb820bd91969e492044e1822f4)
2 files changed