Change defaults for ScrollIntoViewOptions to start/nearest.

This patch changes the defaults for ScrollIntoView Options from
center/center to start/nearest to match the spec.
https://drafts.csswg.org/cssom-view/#extension-to-the-element-interface

Bug: 764282
Change-Id: If6616039cc0eb523e7b2dac530c81857e486cffb
Reviewed-on: https://chromium-review.googlesource.com/c/1425858
Reviewed-by: David Bokan <bokan@chromium.org>
Commit-Queue: Sandra Sun <sunyunjia@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624784}
2 files changed