Reduce viewport arguments parsing noise in the DevTools console

The "minimal-ui" argument is ignored, the other parsing errors
have been transformed into warnings.

R=kenneth.r.christiansen@intel.com, pfeldman@chromium.org
BUG=332794

Review URL: https://codereview.chromium.org/133673002

git-svn-id: svn://svn.chromium.org/blink/trunk@164872 bbb929c8-8fbe-4397-9dbb-9b2b20218538