Contributed by Eriq Augustine <eriq.augustine@gmail.com>

chrome/browser/extensions/extension_menu_manager.cc

Index: chrome/browser/extensions/extension_menu_manager.cc
===================================================================
--- chrome/browser/extensions/extension_menu_manager.cc	(revision 117097)
+++ chrome/browser/extensions/extension_menu_manager.cc	(working copy)
@@ -139,8 +139,12 @@
   context_items_[extension_id].push_back(item);
   items_by_id_[item->id()] = item;
 
-  if (item->type() == ExtensionMenuItem::RADIO && item->checked())
-    RadioItemSelected(item);
+  if (item->type() == ExtensionMenuItem::RADIO) {
+    if (item->checked())
+      RadioItemSelected(item);
+    else
+      SanitizeRadioList(context_items_[extension_id]);
+  }
 
   // If this is the first item for this extension, start loading its icon.
   if (first_item)
@@ -158,6 +162,10 @@
     return false;
   parent->AddChild(child);
   items_by_id_[child->id()] = child;
+
+  if (child->type() == ExtensionMenuItem::RADIO)
+    SanitizeRadioList(parent->children());
+
   return true;
 }
 
@@ -201,6 +209,7 @@
     ExtensionMenuItem* taken =
       old_parent->ReleaseChild(child_id, false /* non-recursive search*/);
     DCHECK(taken == child);
+    SanitizeRadioList(old_parent->children());
   } else {
     // This is a top-level item, so we need to pull it out of our list of
     // top-level items.
@@ -217,13 +226,16 @@
       return false;
     }
     list.erase(j);
+    SanitizeRadioList(list);
   }
 
   if (new_parent) {
     new_parent->AddChild(child);
+    SanitizeRadioList(new_parent->children());
   } else {
     context_items_[child->extension_id()].push_back(child);
     child->parent_id_.reset(NULL);
+    SanitizeRadioList(context_items_[child->extension_id()]);
   }
   return true;
 }
@@ -254,6 +266,7 @@
       delete *j;
       list.erase(j);
       result = true;
+      SanitizeRadioList(list);
       break;
     } else {
       // See if the item to remove was found as a descendant of the current
@@ -262,6 +275,7 @@
       if (child) {
         items_removed = child->RemoveAllDescendants();
         items_removed.insert(id);
+        SanitizeRadioList(GetItemById(*child->parent_id())->children());
         delete child;
         result = true;
         break;
@@ -449,6 +463,63 @@
       item->extension_id(), event_name, json_args, profile, GURL());
 }
 
+void ExtensionMenuManager::SanitizeRadioList(
+    const ExtensionMenuItem::List& item_list) {
+  ExtensionMenuItem::List::const_iterator i = item_list.begin();
+  while (i != item_list.end()) {
+    if ((*i)->type() != ExtensionMenuItem::RADIO) {
+      ++i;
+      break;
+    }
+
+    // Uncheck any checked radio items in the run, and at the end reset
+    // the appropriate one to checked. If no check radio items were found,
+    // then check the first radio item in the run.
+    ExtensionMenuItem::List::const_iterator last_checked = item_list.end();
+    ExtensionMenuItem::List::const_iterator radio_run_iter;
+    for (radio_run_iter = i; radio_run_iter != item_list.end();
+        ++radio_run_iter) {
+      if ((*radio_run_iter)->type() != ExtensionMenuItem::RADIO) {
+        break;
+      }
+
+      if ((*radio_run_iter)->checked()) {
+        last_checked = radio_run_iter;
+        (*radio_run_iter)->SetChecked(false);
+      }
+    }
+
+    if (last_checked != item_list.end())
+      (*last_checked)->SetChecked(true);
+    else
+      (*i)->SetChecked(true);
+
+    i = radio_run_iter;
+  }
+}
+
+bool ExtensionMenuManager::ItemUpdated(const ExtensionMenuItem::Id& id) {
+  if (!ContainsKey(items_by_id_, id))
+    return false;
+
+  ExtensionMenuItem* menu_item = GetItemById(id);
+  DCHECK(menu_item);
+
+  if (menu_item->parent_id()) {
+    SanitizeRadioList(GetItemById(*menu_item->parent_id())->children());
+  } else {
+    std::string extension_id = menu_item->extension_id();
+    MenuItemMap::iterator i = context_items_.find(extension_id);
+    if (i == context_items_.end()) {
+      NOTREACHED();
+      return false;
+    }
+    SanitizeRadioList(i->second);
+  }
+
+  return true;
+}
+
 void ExtensionMenuManager::Observe(
     int type,
     const content::NotificationSource& source,