Simplify the MediaGalleriesPlatformAppBrowserTest copyTo tests.

chrome/test/data/extensions/api_test/media_galleries/copy_to_access/test.js

Index: chrome/test/data/extensions/api_test/media_galleries/copy_to_access/test.js
===================================================================
--- chrome/test/data/extensions/api_test/media_galleries/copy_to_access/test.js	(revision 224775)
+++ chrome/test/data/extensions/api_test/media_galleries/copy_to_access/test.js	(working copy)
@@ -2,8 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+CreateDummyWindowToPreventSleep();
+
 chrome.test.runTests([
-  createTest(validCase, getOnwriteendCallbackExpectSuccess),
-  createTest(invalidCase, getOnwriteendCallbackExpectFailure)
+  function validFileCopyToShouldSucceed() {
+    runCopyToTest(validWEBPImageCase, true /* expect success */);
+  },
+  function invalidFileCopyToShouldFail() {
+    runCopyToTest(invalidWEBPImageCase, false /* expect failure */);
+  },
 ]);