allow tests to override selector and rendering options
renamed the html2canvas.canvasContext to h2cRenderContext, it's used by both backends and thus not canvas specific
images loaded through the proxy could hang the preload process if they finish loading through the proxy but then fail to decode and thus don't call the onload handler of the image object.
in case you run the tests in firefox and have firebug installed and active you now get a profiling run of html2canvas ;)
The image loading done in Preload.js used an array to store image src and image object as 2 consecutive entries in that array. Using the src as an index in a hash allows direct instead of a linear search and also allows to store more data. * improved cleanup of images loaded with the proxy * this also adds a timeout for the image loading phase, after that running image requests are aborted and the rendering is started
* normally when exporting jpeg any pixel that was transparent becomes black, make them white * check for window.console.log before use (avoid crash) * html2canvas.Parse: fix missing call to html2canvas.Util.Extend for the given options