diff -r 000000000000 -r 6474c204b198 dom/workers/test/fileReaderSyncErrors_worker.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/workers/test/fileReaderSyncErrors_worker.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,79 @@
+/**
+ * Delegates "is" evaluation back to main thread.
+ */
+function is(actual, expected, message) {
+  var rtnObj = new Object();
+  rtnObj.actual = actual;
+  rtnObj.expected = expected;
+  rtnObj.message = message;
+  postMessage(rtnObj);
+}
+
+/**
+ * Tries to write to property.
+ */
+function writeProperty(file, property) {
+  try {
+    var oldValue = file[property];
+    file[property] = -1;
+    is(false, true, "Should have thrown an exception setting a read only property.");
+  } catch (ex) {
+    is(true, true, "Should have thrown an exception setting a read only property.");
+  }
+}
+
+/**
+ * Passes junk arguments to FileReaderSync methods and expects an exception to
+ * be thrown.
+ */
+function fileReaderJunkArgument(blob) {
+  var fileReader = new FileReaderSync();
+
+  try {
+    fileReader.readAsBinaryString(blob);
+    is(false, true, "Should have thrown an exception calling readAsBinaryString.");
+  } catch(ex) {
+    is(true, true, "Should have thrown an exception.");
+  }
+
+  try {
+    fileReader.readAsDataURL(blob);
+    is(false, true, "Should have thrown an exception calling readAsDataURL.");
+  } catch(ex) {
+    is(true, true, "Should have thrown an exception.");
+  }
+
+  try {
+    fileReader.readAsArrayBuffer(blob);
+    is(false, true, "Should have thrown an exception calling readAsArrayBuffer.");
+  } catch(ex) {
+    is(true, true, "Should have thrown an exception.");
+  }
+
+  try {
+    fileReader.readAsText(blob);
+    is(false, true, "Should have thrown an exception calling readAsText.");
+  } catch(ex) {
+    is(true, true, "Should have thrown an exception.");
+  }
+}
+
+onmessage = function(event) {
+  var file = event.data;
+
+  // Test read only properties.
+  writeProperty(file, "size");
+  writeProperty(file, "type");
+  writeProperty(file, "name");
+  writeProperty(file, "mozFullPath");
+
+  // Bad types.
+  fileReaderJunkArgument(undefined);
+  fileReaderJunkArgument(-1);
+  fileReaderJunkArgument(1);
+  fileReaderJunkArgument(new Object());
+  fileReaderJunkArgument("hello");
+
+    // Post undefined to indicate that testing has finished.
+  postMessage(undefined);
+};