Moved remaining legacy viewport tests to unit tests.

In https://codereview.chromium.org/48613005/ most of the legacy viewport
meta tag tests were converted into unit tests. This CL moves the
remaining "trickier" tests.

BUG=314001

Review URL: https://codereview.chromium.org/99223005

git-svn-id: svn://svn.chromium.org/blink/trunk@163034 bbb929c8-8fbe-4397-9dbb-9b2b20218538