diff -r 000000000000 -r 6474c204b198 dom/workers/test/fileSlice_worker.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/workers/test/fileSlice_worker.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,27 @@
+/**
+ * Expects an object containing a blob, a start offset, an end offset
+ * and an optional content type to slice the blob. Returns an object
+ * containing the size and type of the sliced blob.
+ */
+onmessage = function(event) {
+  var blob = event.data.blob;
+  var start = event.data.start;
+  var end = event.data.end;
+  var contentType = event.data.contentType;
+
+  var slicedBlob;
+  if (contentType == undefined && end == undefined) {
+    slicedBlob = blob.slice(start);
+  } else if (contentType == undefined) {
+    slicedBlob = blob.slice(start, end);
+  } else {
+    slicedBlob = blob.slice(start, end, contentType);
+  }
+
+  var rtnObj = new Object();
+
+  rtnObj.size = slicedBlob.size;
+  rtnObj.type = slicedBlob.type;
+
+  postMessage(rtnObj);
+};