Import FileAPI tests from web-platform-tests

LayoutTests/imported/web-platform-tests/FileAPI/FileReaderSync.worker.js

+importScripts("/resources/testharness.js");
+
+var blob, readerSync;
+setup(function() {
+  readerSync = new FileReaderSync();
+  blob = new Blob(["test"]);
+});
+
+test(function() {
+  assert_true(readerSync instanceof FileReaderSync);
+}, "Interface");
+
+test(function() {
+  var text = readerSync.readAsText(blob);
+  assert_equals(text, "test");
+}, "readAsText");
+
+test(function() {
+  var data = readerSync.readAsDataURL(blob);
+  assert_equals(data.indexOf("data:"), 0);
+}, "readAsDataURL");
+
+test(function() {
+  var data = readerSync.readAsArrayBuffer(blob);
+  assert_true(data instanceof ArrayBuffer);
+}, "readAsArrayBuffer");
+
+done();