spec: browser default sizing test

Change-Id: I549fa7dd46fb0676195fb6c7f17f55a71886f709
Reviewed-on: https://gerrit.instructure.com/36781
Reviewed-by: Bryan Madsen <bryan@instructure.com>
Product-Review: Bryan Madsen <bryan@instructure.com>
QA-Review: Bryan Madsen <bryan@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>