Call async test functions with await to better catch exceptions

Currently any exceptions thrown in an async test function are not caught
and the test will fail as a timeout.

Added fix for GalleryJsTest.ImageViewTest which was throwing exceptions
with undeclared metrics.record... functions.

TBR=fukino@chromium.org

Change-Id: I40ed5ff91a35ffd9a1c399d4d8405554e3fab911
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2459136
Commit-Queue: Joel Hockey <joelhockey@chromium.org>
Auto-Submit: Joel Hockey <joelhockey@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816044}

ui/file_manager/gallery/js/image_editor/image_view_unittest.js

@@ -2,6 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// eslint-disable-next-line no-var
+var metrics = {
+  recordEnum: function() {},
+  recordInterval: function() {},
+  startInterval: function() {}
+};
+
+
 function testImageView() {
   const mockFileSystem = new MockFileSystem('volumeId');
   const mockEntry = MockFileEntry.create(mockFileSystem, '/test.jpg');

ui/webui/resources/js/webui_resource_test.js

@@ -243,7 +243,7 @@ function startTesting() {
  * @param {boolean=} opt_asyncTestFailure Optional parameter indicated if the
  *     last asynchronous test failed.
  */
-function continueTesting(opt_asyncTestFailure) {
+async function continueTesting(opt_asyncTestFailure) {
   const now = performance.now();
   if (testName) {
     console.log(
@@ -270,7 +270,7 @@ function continueTesting(opt_asyncTestFailure) {
         testHarness.setUp();
       }
       pendingTearDown = testHarness.tearDown || null;
-      testScope[testName](continueTesting);
+      await testScope[testName](continueTesting);
     } catch (err) {
       console.error('Failure in test ' + testName + '\n' + err);
       console.log(err.stack);