WebStateList is an array of web::WebState* wrappers.

ios/shared/chrome/browser/tabs/web_state_handle.h

+// Copyright 2017 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_SHARED_CHROME_BROWSER_TABS_WEB_STATE_HANDLE_H_
+#define IOS_SHARED_CHROME_BROWSER_TABS_WEB_STATE_HANDLE_H_
+
+namespace web {
+class WebState;
+class WebStateImpl;
+}
+
+// Wraps a web::WebState instance in an Objective-C instance. Allows using
+// Objective-C collection to reference web::WebStates.
+@protocol WebStateHandle
+
+// Returns the wrapped web::WebState.
+@property(nonatomic, readonly) web::WebState* webState;
+
+// Returns the wrapped web::WebState as a web::WebStateImpl. Deprecated,
+// use webState instead if possible.
+@property(nonatomic, readonly) web::WebStateImpl* webStateImpl;
+
+@end
+
+#endif  // IOS_SHARED_CHROME_BROWSER_TABS_WEB_STATE_HANDLE_H_