Upstream Chrome on iOS source code [5/11].

ios/chrome/browser/ui/material_components/app_bar_presenting.h

+// Copyright 2016 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_CHROME_BROWSER_UI_MATERIAL_COMPONENTS_APP_BAR_PRESENTING_H_
+#define IOS_CHROME_BROWSER_UI_MATERIAL_COMPONENTS_APP_BAR_PRESENTING_H_
+
+#import <UIKit/UIKit.h>
+
+@class MDCAppBar;
+
+// An object conforming to this protocol is capable of creating and managing an
+// MDCAppBar. Typically, UIViewController's can implement this protocol to vend
+// the app bar they can optionally be presenting.
+@protocol AppBarPresenting<NSObject>
+
+// The installed app bar, if any.
+@property(nonatomic, readonly) MDCAppBar* appBar;
+
+@end
+
+#endif  // IOS_CHROME_BROWSER_UI_MATERIAL_COMPONENTS_APP_BAR_PRESENTING_H_