Tests huge image scaling when viewport is enabled. Requires DumpRenderTree.
To manual test, open resources/5000x5000.png in a viewport-capable browser (e.g. on Android or enable viewport emulation in DevTools).
Passes if the image shinks to fit the width.

viewport meta: <meta name="viewport" content="width=device-width, minimum-scale=0.1">
image style: -webkit-user-select: none;cursor: zoom-in;
image actual width: 100