Got rid of the internal copies of webview attributes.

extensions/test/data/web_view/apitest/main.js

Index: extensions/test/data/web_view/apitest/main.js
diff --git a/extensions/test/data/web_view/apitest/main.js b/extensions/test/data/web_view/apitest/main.js
index 1287723c26f0e1a008f9ad2ffe116983b063f07c..6656e0540fc8f175d20c77621bb38999dcbb0878 100644
--- a/extensions/test/data/web_view/apitest/main.js
+++ b/extensions/test/data/web_view/apitest/main.js
@@ -1282,21 +1282,17 @@ function testOnEventProperties() {
   document.body.appendChild(webview);
 }
 
-// This test verifies that setting the partition attribute after the src has
-// been set raises an exception.
-function testPartitionRaisesException() {
+// This test verifies that the partion attribute cannot be changed after the src
+// has been set.
+function testPartitionChangeAfterNavigation() {
   var webview = document.createElement('webview');
   var partitionAttribute = arguments.callee.name;
   webview.setAttribute('partition', partitionAttribute);
 
   var loadstopHandler = function(e) {
-    try {
-      webview.partition = 'illegal';
-      embedder.test.fail();
-    } catch (e) {
-      embedder.test.assertEq(partitionAttribute, webview.partition);
-      embedder.test.succeed();
-    }
+    webview.partition = 'illegal';
+    embedder.test.assertEq(partitionAttribute, webview.partition);
+    embedder.test.succeed();
   };
   webview.addEventListener('loadstop', loadstopHandler);
 
@@ -1707,7 +1703,7 @@ embedder.test.testList = {
   'testNewWindowNoReferrerLink': testNewWindowNoReferrerLink,
   'testNewWindowTwoListeners': testNewWindowTwoListeners,
   'testOnEventProperties': testOnEventProperties,
-  'testPartitionRaisesException': testPartitionRaisesException,
+  'testPartitionChangeAfterNavigation': testPartitionChangeAfterNavigation,
   'testPartitionRemovalAfterNavigationFails':
       testPartitionRemovalAfterNavigationFails,
   'testReassignSrcAttribute': testReassignSrcAttribute,