Fix a couple of types.

Author: Sepand Parhami

src/testing/animation-test-controller.ts

@@ -123,9 +123,9 @@ const createStopperStyle = function(): HTMLStyleElement {
 
 /**
  * After function calls to obj[prop], calls the callback with the return value.
- * @param {!Object} obj
- * @param {string} prop
- * @param {function(*)} callback
+ * @param obj
+ * @param prop
+ * @param callback
  */
 function after(obj: Object, prop: string, callback: Function) {
   if (!(prop in obj)) {

src/testing/utils.ts

@@ -14,12 +14,12 @@
  * limitations under the License.
  */
 
-export async function imgLoadPromise(img) {
+ export async function imgLoadPromise(img: HTMLImageElement): Promise<void> {
   if (img.complete) {
     return;
   }
 
-  return new Promise((resolve, reject) => {
+  return new Promise<void>((resolve, reject) => {
     function finish() {
       img.removeEventListener('load', load);
       img.removeEventListener('error', error);
@@ -38,4 +38,4 @@ export async function imgLoadPromise(img) {
     img.addEventListener('load', load);
     img.addEventListener('error', error);
   });
-}
+}