Switch AutofillManager to be UserData on WebContents.

base/supports_user_data.h

Index: base/supports_user_data.h
diff --git a/base/supports_user_data.h b/base/supports_user_data.h
index 4c7cdcad26202bb5577f31013a01f1a0587afa36..77367553daf5b405d5fffa138614d6a64b0234f0 100644
--- a/base/supports_user_data.h
+++ b/base/supports_user_data.h
@@ -62,9 +62,9 @@ template <typename T>
 class UserDataAdapter : public base::SupportsUserData::Data {
  public:
   static T* Get(SupportsUserData* supports_user_data, const char* key) {
-   UserDataAdapter* data =
+    UserDataAdapter* data =
       static_cast<UserDataAdapter*>(supports_user_data->GetUserData(key));
-    return static_cast<T*>(data->object_.get());
+    return data ? static_cast<T*>(data->object_.get()) : NULL;
   }
 
   UserDataAdapter(T* object) : object_(object) {}