CB-6994 - Windows 8 does not save big file transferred using Blob

When trying to save Blob using FileWriter.write method, if the blob's size is too high, we get a stack overflow exception during the conversion of the blob into an basic array.

In order to avoid this exception, we pass the Blob or File directly in FileProxy (avoid the conversion to ArrayBuffer) and we use a specific method in FileProxy to save the Blob directly to the filesystem by using Streams (safe).

More info at : https://issues.apache.org/jira/browse/CB-6994
In my case it fails with InvalidStateError. But the following code works. Pls double check
if (data instanceof ArrayBuffer) {
    //var dataView = new DataView(data);
    //var data2 = new Blob([dataView]);
    data = new Blob([data]);
}

I see similar code is used in the following test
http://jsperf.com/array-buffer-blob