Introduce the WebState iOS provider interface.

ios/public/provider/web/web_state.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_H_
+#define IOS_PUBLIC_PROVIDER_WEB_WEB_STATE_H_
+
+#include "ios/public/consumer/base/supports_user_data.h"
+
+namespace ios {
+
+// Core interface for interaction with the web.
+class WebState : public ios::SupportsUserData {
+ public:
+  virtual ~WebState() {}
+
+ protected:
+  WebState() {}
+};
+
+}  // namespace ios
+
+#endif  // IOS_PUBLIC_PROVIDER_WEB_WEB_STATE_H_