Revert "Revert 159282 "Refactor fixed layout mode""
Revert "Disable NoWideViewportAndScaleLessThanOneWithDeviceWidth."

This reverts r159581 and r159594. The revert was bad and caused
a webkit_unit_test and a layout test to fail. See the bug for details.

BUG=306566
TBR=vollick@chromium.org

Review URL: https://codereview.chromium.org/27037006

git-svn-id: svn://svn.chromium.org/blink/trunk@159604 bbb929c8-8fbe-4397-9dbb-9b2b20218538