Resize the viewport to <width> x <height> then save a screenshot.
When (I |we )*save (\d+) x (\d+) screenshot
Example #1: When I save 1440 x 900 screenshot
Example #2: When we save 1200 x 800 screenshot
Example #3:
Given I am on "/about-us"
When I save 1440 x 900 screenshot