Use arrow functions for callbacks.

This is an automated change to convert use of "function" functions
to arrow functions.  This doesn't change all uses of bind() that
could be converted.  This also doesn't remove all "function" functions.

Change-Id: I40ac7d086bcef947a1be083359c8fd1d4499a9c3

test/util/array_utils_unit.js

@@ -15,10 +15,10 @@
  * limitations under the License.
  */
 
-describe('ArrayUtils', function() {
+describe('ArrayUtils', () => {
   const ArrayUtils = shaka.util.ArrayUtils;
 
-  describe('hasSameElements', function() {
+  describe('hasSameElements', () => {
     it('determines same elements', () => {
       expectEqual([], []);
       expectEqual([1, 2, 3], [1, 2, 3]);