[ShareCCT] Check for window destroyed

Sharing intent to Android should be halted when the Android window is
being destroyed.

This can happen during Sharing in CCT.

Bug: 41496820
Change-Id: I4079d559b20ec06c6d296ec5e48aab138e4c48ee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5973393
Commit-Queue: Wenyu Fu <wenyufu@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Auto-Submit: Hailey Wang <haileywang@google.com>
Reviewed-by: Wenyu Fu <wenyufu@chromium.org>
Commit-Queue: Hailey Wang <haileywang@google.com>
Cr-Commit-Position: refs/heads/main@{#1374831}