function createZeroArray(len) {
    var arr = [];
    for (var i = 0; i < len; i++) {
        arr[i] = 0;
    }
    return arr;
}
Mainly do the parse and compile of shader string
Support shader code chunk import and export
Support shader semantics
http://www.nvidia.com/object/using_sas.html
https://github.com/KhronosGroup/collada2json/issues/45