Upstream iOS web API.

ios/public/provider/web/web_state_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_PROVIDER_WEB_WEB_STATE_USER_DATA_H_
-#define IOS_PUBLIC_PROVIDER_WEB_WEB_STATE_USER_DATA_H_
-
-#include "base/supports_user_data.h"
-#include "ios/public/provider/web/web_state.h"
-
-namespace ios {
-
-// A base class for classes attached to, and scoped to, the lifetime of a
-// WebState. For example:
-//
-// --- in foo.h ---
-// class Foo : public ios::WebStateUserData<Foo> {
-//  public:
-//   virtual ~Foo();
-//   // ... more public stuff here ...
-//  private:
-//   explicit Foo(ios::WebState* web_state);
-//   friend class ios::WebStateUserData<Foo>;
-//   // ... more private stuff here ...
-// }
-// --- in foo.cc ---
-// DEFINE_WEB_CONTENTS_USER_DATA_KEY(Foo);
-//
-template <typename T>
-class WebStateUserData : public base::SupportsUserData::Data {
- public:
-  // Creates an object of type T, and attaches it to the specified WebState.
-  // If an instance is already attached, does nothing.
-  static void CreateForWebState(WebState* web_state) {
-    if (!FromWebState(web_state))
-      web_state->SetUserData(UserDataKey(), new T(web_state));
-  }
-
-  // Retrieves the instance of type T that was attached to the specified
-  // WebState (via CreateForWebState above) and returns it. If no instance
-  // of the type was attached, returns NULL.
-  static T* FromWebState(WebState* web_state) {
-    return static_cast<T*>(web_state->GetUserData(UserDataKey()));
-  }
-  static const T* FromWebState(const WebState* web_state) {
-    return static_cast<const T*>(web_state->GetUserData(UserDataKey()));
-  }
-
- protected:
-  static inline void* UserDataKey() {
-    return &kLocatorKey;
-  }
-
- private:
-  // The user data key.
-  static int kLocatorKey;
-};
-
-// The macro to define the locator key. This key should be defined in the .cc
-// file of the derived class.
-//
-// The "= 0" is surprising, but is required to effect a definition rather than
-// a declaration. Without it, this would be merely a declaration of a template
-// specialization. (C++98: 14.7.3.15; C++11: 14.7.3.13)
-//
-#define DEFINE_WEB_STATE_USER_DATA_KEY(TYPE) \
-template<>                                      \
-int ios::WebStateUserData<TYPE>::kLocatorKey = 0
-
-}  // namespace ios
-
-#endif  // IOS_PUBLIC_PROVIDER_WEB_WEB_STATE_USER_DATA_H_