new Image() used a bare class shim with no .style, so new Image().style
returned undefined and libraries touching style on a detached image threw
(issue #350). Build the image from document.createElement('img') instead,
which gives a working CSSStyleDeclaration, attribute reflection, and event
dispatch. Assigning .src still emulates a successful decode: it flips
complete and fires load (both the onload property and load listeners) so
lazy loaders and preloaders do not hang.