Improve <adview> implementation and add tests.

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

Index: chrome/test/data/extensions/platform_apps/ad_view/src_not_exposed/chrometest.js
diff --git a/chrome/test/data/extensions/platform_apps/ad_view/src_not_exposed/chrometest.js b/chrome/test/data/extensions/platform_apps/ad_view/src_not_exposed/chrometest.js
new file mode 100644
index 0000000000000000000000000000000000000000..9fcce3492bee65b097e8356a41812df1da5ce243
--- /dev/null
+++ b/chrome/test/data/extensions/platform_apps/ad_view/src_not_exposed/chrometest.js
@@ -0,0 +1,20 @@
+// 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 adview = document.getElementsByTagName("adview")[0];
+
+  // Act
+
+  // Assert
+  adview.addEventListener("loadcommit", function(e){
+    chrome.test.assertEq(false, adview.hasAttribute("src"));
+    chrome.test.assertEq(null, adview.getAttribute("src"));
+    chrome.test.assertEq(undefined, adview['src']);
+    chrome.test.assertEq(undefined, adview.src);
+    chrome.test.sendMessage("test-finished");
+  });
+  adview.setAttribute('ad-network', 'admob');
+});