Reverting changes that made window.scroll properties relative to the layout viewport.

Reason for revert:
Broke a bunch of sites that relied on visual viewport coordinates
(see www.crbug.com/571297). Reverting temporary until a new api that provides visual
viewport coordinates is made available to developers.

Revert "Make window.scroll properties relative to the layout viewport by default."

This reverts commit f75faf53de4a5c59269143b6edbfc6dc40c7fb33.

Revert "Remove plumbing for the inert-visual-viewport flag."

This reverts commit 58d42ae1d6690a9f625e23f160b346e9cebeab01.

TBR=avi@chromium.org,kenrb@chromium.org
BUG=571297

Review URL: https://codereview.chromium.org/1712743002

Cr-Commit-Position: refs/heads/master@{#376742}
(cherry picked from commit 835268c26a1f84e944b70d69703a54c4cb50bc5b)

Review URL: https://codereview.chromium.org/1724103002 .

Cr-Commit-Position: refs/branch-heads/2623@{#475}
Cr-Branched-From: 92d77538a86529ca35f9220bd3cd512cbea1f086-refs/heads/master@{#369907}
23 files changed