Stretch image in iron-image element

Question

I have an element inside a div :

. The image is 315px in width

Answer 1

I also wanted to update "img" tag style which is "under" (=shadow DOM) the iron-image.

To do so I have updated the style, here is the dart code:

querySelectorAll('img').forEach((Element img) {
img.setAttribute('style', 'width:330px;height:auto');
});

This code is placed within the PolymerElement "attached" available function (wouldn't work in the "ready" function)

attached Called after the element is attached to the document.