Revert "Revert "Check that ViewTreeObserver is alive before unregistering listener.""

This reverts commit 4948a474ce4dd7b43edb788308d35b866173ab5a.

Reason for revert: The performance regression was caused by a different change.

Bug: 113260844
Change-Id: I0f963f04f9d90b2d6eb5937f7778e9726fc381cc
1 file changed