<script src="lib/WMAppCacheProxy.js"></script>
<script>
WMAppCacheProxy.createProxyURL(url, mimeType, function(err, blobURL){
    console.log(blobURL);
});
</script>

importScripts("lib/WMAppCacheProxy.js");

WMAppCacheProxy.createProxyURL(url, mimeType, function(err, blobURL){
    console.log(blobURL);
});