Adds diagnostic logging for LongScreenshotActivity

This adds logging of dimensions and positions of
crop handles after a long screenshot capture.

Switches to OneShotPreDrawListener where appropriate
to improve readability.

Bug: 232633995
Test: logging only change; manually, take long screenshot
      crop, save, observe result, verify results match
Change-Id: I699f8d69b78e89a7a5364fda84bc4d6316b77d31