FWB: Custom scrolling values 1/2

ported/modified from https://gerrit.omnirom.org/#/c/4251/
originally written by Yanuar Harry <ai.the.smarties.physics@gmail.com>

AICP:
PS2: fix build
PS3: Use default values as defaults

Change-Id: I7f23fe736507f836137c5d6dc0b5fd2ad4a95462