Make the WebContentsUserData locator key private.

content/public/browser/web_contents_user_data.h

Index: content/public/browser/web_contents_user_data.h
diff --git a/content/public/browser/web_contents_user_data.h b/content/public/browser/web_contents_user_data.h
index 9dfe170cddd81d586d11774b6af1d7458d1c87d5..a65ec84cf9c2bc3c8e6b813ef06103822a240d76 100644
--- a/content/public/browser/web_contents_user_data.h
+++ b/content/public/browser/web_contents_user_data.h
@@ -35,7 +35,7 @@ class WebContentsUserData : public base::SupportsUserData::Data {
   static void CreateForWebContents(WebContents* contents) {
     DCHECK(contents);
     if (!FromWebContents(contents))
-      contents->SetUserData(&kLocatorKey, new T(contents));
+      contents->SetUserData(UserDataKey(), new T(contents));
   }
 
   // Retrieves the instance of type T that was attached to the specified
@@ -43,13 +43,19 @@ class WebContentsUserData : public base::SupportsUserData::Data {
   // of the type was attached, returns NULL.
   static T* FromWebContents(WebContents* contents) {
     DCHECK(contents);
-    return static_cast<T*>(contents->GetUserData(&kLocatorKey));
+    return static_cast<T*>(contents->GetUserData(UserDataKey()));
   }
   static const T* FromWebContents(const WebContents* contents) {
     DCHECK(contents);
-    return static_cast<const T*>(contents->GetUserData(&kLocatorKey));
+    return static_cast<const T*>(contents->GetUserData(UserDataKey()));
   }
 
+ protected:
+  static inline void* UserDataKey() {
+    return &kLocatorKey;
+  }
+
+ private:
   // The user data key.
   static int kLocatorKey;
 };