[MD Extensions] Update subpages when the backing extension data changes

chrome/test/data/webui/extensions/extension_manager_test.js

Index: chrome/test/data/webui/extensions/extension_manager_test.js
diff --git a/chrome/test/data/webui/extensions/extension_manager_test.js b/chrome/test/data/webui/extensions/extension_manager_test.js
index 5e99cf68e4078a7307230eba431a76fa01fa08fd..9b93e8af1c196747af71594729d6b87476aa5a4e 100644
--- a/chrome/test/data/webui/extensions/extension_manager_test.js
+++ b/chrome/test/data/webui/extensions/extension_manager_test.js
@@ -11,6 +11,7 @@ cr.define('extension_manager_tests', function() {
     ShowItems: 'show items',
     ChangePages: 'change pages',
     UrlNavigationToDetails: 'url navigation to details',
+    UpdateItemData: 'update item data',
   };
 
   function getDataByName(list, name) {
@@ -159,6 +160,47 @@ cr.define('extension_manager_tests', function() {
         var detailsView = manager.$['details-view'];
         expectEquals('ldnnhddmnhbkjipkidpdiheffobcpfmf', detailsView.data.id);
       });
+
+      test(assert(TestNames.UpdateItemData), function() {
+        var oldDescription = 'old description';
+        var newDescription = 'new description';
+        var extension = extension_test_util.createExtensionInfo(
+            {description: oldDescription});
+        var secondExtension = extension_test_util.createExtensionInfo({
+            description: 'irrelevant',
+            id: 'b'.repeat(32),
+        });
+        manager.addItem(extension);
+        manager.addItem(secondExtension);
+        var data = manager.extensions[0];
+        manager.showItemDetails(extension);
+        var detailsView = manager.$['details-view'];
+        expectEquals(extension.id, detailsView.data.id);
+        expectEquals(oldDescription, detailsView.data.description);
+        expectEquals(
+            oldDescription,
+            detailsView.$$('.section .section-content').textContent.trim());
+
+        var extensionCopy = Object.assign({}, extension);
+        extensionCopy.description = newDescription;
+        manager.updateItem(extensionCopy);
+        expectEquals(extension.id, detailsView.data.id);
+        expectEquals(newDescription, detailsView.data.description);
+        expectEquals(
+            newDescription,
+            detailsView.$$('.section .section-content').textContent.trim());
+
+        // Updating a different extension shouldn't have any impact.
+        var secondExtensionCopy = Object.assign({}, secondExtension);
+        secondExtensionCopy.description = 'something else';
+        manager.updateItem(secondExtensionCopy);
+        expectEquals(extension.id, detailsView.data.id);
+        expectEquals(newDescription, detailsView.data.description);
+        expectEquals(
+            newDescription,
+            detailsView.$$('.section .section-content').textContent.trim());
+
+      });
     });
   }