The neat thing about using the link is that I can send it to non-techs for previewing websites in different resolutions.

Unfortunately less complete, because it resizes the browser window globally (outer size here). With tree-style tabs it doesn't match what many will see.

No, actually the web developer extension allows either the entire window or the portal (page display) dimensions to be specified.

In what browser? For Chrome, it appears to resize the outer window, not the viewport.

Firefox. I guess I never used that feature in Chrome...

I see, now. The Chrome version will report the viewport size but does not appear to offer the ability to set it.

Sorry, I was not entirely right.

The Web Developer extension for Firefox asks for width x height dimensions plus an extra "viewport" checkbox, anywhere you specify the size.