Move corner handles closer to task's rounded corners.

Moves handles closer to task bounds and adds a distance check to
ensure mouse inputs don't register as corner inputs beyond a certain
distance.

Video: http://recall/-/eKxklN4CHu7YvO9E4ZpRD8/fr7SEzvdJQY0NiKj8RTa17
Bug: 280827642
Test: Manual
Change-Id: Ibdf35767ad8b6196e85fab13372dc7bb3424f738