Improve <adview> implementation and add tests.

chrome/test/data/extensions/platform_apps/ad_view/properties_exposed/chrometest.js

Index: chrome/test/data/extensions/platform_apps/ad_view/properties_exposed/chrometest.js
diff --git a/chrome/test/data/extensions/platform_apps/ad_view/properties_exposed/chrometest.js b/chrome/test/data/extensions/platform_apps/ad_view/properties_exposed/chrometest.js
new file mode 100644
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+++ b/chrome/test/data/extensions/platform_apps/ad_view/properties_exposed/chrometest.js
@@ -0,0 +1,29 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+chrome.test.getConfig(function(config) {
+  // Arrange
+  var guestURL = 'http://localhost:' + config.testServer.port +
+      '/files/extensions/platform_apps/ad_view/ad_network_site/testsdk.html';
+  var adview = document.getElementsByTagName('adview')[0];
+  var adnetwork = adview.getAttribute('ad-network');
+
+  // Act
+  adview.setAttribute('src', guestURL);
+
+  // Assert
+  // Note: Assertions have to occur in a callback function because of the
+  //  way mutation events are processed. See
+  //  http://lists.w3.org/Archives/Public/public-webapps/2011JulSep/1622.html
+  setTimeout(function() {
+    chrome.test.assertEq(guestURL, adview.getAttribute('src'));
+    chrome.test.assertEq(guestURL, adview['src']);
+    chrome.test.assertEq(guestURL, adview.src);
+
+    chrome.test.assertEq(adnetwork, adview.getAttribute('ad-network'));
+    chrome.test.assertEq(adnetwork, adview['ad-network']);
+    //chrome.test.assertEq(adnetwork, adview.ad-network);
+    chrome.test.sendMessage('test-finished');
+  }, 0);
+});