Ignore viewport meta tags when Request Desktop Site is enabled.

This matches desktop Chrome, and it applies the default
"min-width: 980px;" in viewportAndroid.css -- putting responsive
pages into their desktop/tablet layout.

The enableViewport/enableMetaViewport settings distinction had
bit-rotted somewhat since they've always been the same value
(in fact disabling the latter setting didn't actually drop support
for it) so I needed to do some cleanup there as well.


Review URL: https://codereview.chromium.org/1785953002

Cr-Commit-Position: refs/heads/master@{#386313}
18 files changed