Moved main frame resize to happen outside refreshPageScaleFactor.

refreshPageScaleFactor only gets called if the page scale constraints are dirty.
This happens when the page changes width but not when the height changes. This
cuased a bug where changing the window height only wouldn't resize the main
frame/outer viewport.

BUG=370218

Review URL: https://codereview.chromium.org/271593005

git-svn-id: svn://svn.chromium.org/blink/trunk@173672 bbb929c8-8fbe-4397-9dbb-9b2b20218538