Fix coordinate space issues in scroll.js
Fix coordinate space issues in scroll.js

In Chromium r506804, I changed all gpuBenchmarking methods to expect
input arguments to be in screen/viewport coordinates. That is, they
should track the "finger on the glass" rather than Elements on the
page. Thus, they're invariant under pinch-zoom.

However, I missed a few callsites in Catapult, scroll.js being one of
them. Since gpuBenchmarking no longer applies the pageScaleFactor to the
scroll distance, scroll.js must now do it itself.

I've also cleaned how scroll distances are calculated in light of the
"inert-visual-viewport" changes that shipped in M61. Namely, that
the scrollTop value from body/window doesn't reflect the visualViepwort
any more.

Bug: chromium:772447
Change-Id: Ia4a55e1b5aa16a9c0c624d78f892e3299398b447
Reviewed-on: https://chromium-review.googlesource.com/711159
Reviewed-by: Ned Nguyen <8e49e083cfcfb68517585b2e78d68c2fd2b70562@google.com>
Commit-Queue: David Bokan <9e5676d47d19eb72262e56b54b7e780c7d70af34@chromium.org>

catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult