Attach IME screenshot to non-app main window

In case when dismissing dialog styled application window
can see the IME animated with fade-out as a part of the dialog.

Bug: 201139553
Bug: 212570341
Test: manual as steps with launching a dialog:
   1) Launch Settings -> Network & internet -> Private DNS
   2) Tap the editor to show IME
   3) Press Cancel button to see if IME screenshot is anmating

Change-Id: Ib4c38736908be52f8cbcfe522f4515c5b9aa4e63