The font size in DomDistiller preference was linked with accessibility
scaling. Now it links with local scaling, which can also be adjusted by
pinch-to-zoom gesture. The local scaling syncs across tabs.

This local scaling doesn't sync across devices by design.

BUG=445632, 464822
TEST=browser_tests --gtest_filter="DomDistiller*"

Review URL: https://codereview.chromium.org/1225183002

Cr-Commit-Position: refs/heads/master@{#350976}