<third_party/WebKit> Apply Qt defaults to scroll animations

This patch applies the Qt scroll animation configuration from WebKit.
This makes the scrolling more responsive and smooth when used with
touchpad scroll gestures or free spinning scroll wheels.

Change-Id: I2f17185f3e95c6bc84608cc4c3945dba2d67faa8
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>