* The extension content drives the sizing of the browser and popup that contains it via the Extension:BrowserResized message. The ignoreResizes property throttles/debounces this initially, stashing the dimensions received rather than triggering resize of the popup for every message. When the popup is a subview and fixedWidth, we ignore width but *do* want to use the stashed height value.
* Until the panel is given visibility, it has 0 height, so after setting visibility, wait until the next refresh-driver tick before measuring any header which should get added to the overall view height
MozReview-Commit-ID: AgcruVb9QPA
cd8e6dc737
