Cleanup WebState and WebStateUserData API

ios/public/consumer/base/supports_user_data.h

-// Copyright 2013 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef IOS_PUBLIC_CONSUMER_BASE_SUPPORTS_USER_DATA_H_
-#define IOS_PUBLIC_CONSUMER_BASE_SUPPORTS_USER_DATA_H_
-
-namespace ios {
-
-class SupportsUserDataInternal;
-
-// This is a helper for classes that want to allow users to stash random data by
-// key. At destruction all the objects will be destructed.
-class SupportsUserData {
- public:
-  SupportsUserData();
-
-  // Derive from this class and add your own data members to associate extra
-  // information with this object. Alternatively, add this as a public base
-  // class to any class with a virtual destructor.
-  class Data {
-   public:
-    virtual ~Data() {}
-  };
-
-  // The user data allows the clients to associate data with this object.
-  // Multiple user data values can be stored under different keys.
-  // This object will TAKE OWNERSHIP of the given data pointer, and will
-  // delete the object if it is changed or the object is destroyed.
-  Data* GetUserData(const void* key) const;
-  void SetUserData(const void* key, Data* data);
-  void RemoveUserData(const void* key);
-
-  // SupportsUserData is not thread-safe, and on debug build will assert it is
-  // only used on one thread. Calling this method allows the caller to hand
-  // the SupportsUserData instance across threads. Use only if you are taking
-  // full control of the synchronization of that handover.
-  void DetachUserDataThread();
-
- protected:
-  virtual ~SupportsUserData();
-
- private:
-  // Owned by this object and scoped to its lifetime.
-  SupportsUserDataInternal* internal_helper_;
-};
-
-}  // namespace ios
-
-#endif  // IOS_PUBLIC_CONSUMER_BASE_SUPPORTS_USER_DATA_H_