Avoid overflow in focus fudge calculation

When comparing decoding the next View to get focus, the last-resort
calculation (magic number and square of distance between the View
corners) could overflow, giving a false positive. This causes the
focus to jump around in certain cases. Change from int to long to
avoid in the foreseeable future.

Test: Manual
- Use a phone with an 18:9 ratio (1080*2160)
- make FrameworksCoreTests
- adb install -r out/target/product/aurora/data/app/FrameworksCoreTests/FrameworksCoreTests.apk
- adb shell am instrument -r -w -e class android.widget.scroll.ScrollViewButtonsAndLabelsTest#testArrowScrollUpOffScreenVerticalFadingEdge com.android.frameworks.coretests/android.support.test.runner.AndroidJUnitRunner
Change-Id: I119cd66f563cfa312c2304bb910c27075e674e59