[Navigation Experiment] Add WKBasedNavigationManagerImpl.

ios/web/web_state/ui/crw_web_view_navigation_proxy.h

Index: ios/web/web_state/ui/crw_web_view_navigation_proxy.h
diff --git a/ios/web/web_state/ui/crw_web_view_navigation_proxy.h b/ios/web/web_state/ui/crw_web_view_navigation_proxy.h
new file mode 100644
index 0000000000000000000000000000000000000000..0d6fb4080a7549f69e945ca75e772a629656ce35
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+++ b/ios/web/web_state/ui/crw_web_view_navigation_proxy.h
@@ -0,0 +1,26 @@
+// 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_WEB_WEB_STATE_UI_WEB_VIEW_NAVIGATION_PROXY_H_
+#define IOS_WEB_WEB_STATE_UI_WEB_VIEW_NAVIGATION_PROXY_H_
+
+#import <WebKit/WebKit.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+// A protocol to expose a subset of the WKWebView API to NavigationManager.
+@protocol CRWWebViewNavigationProxy
+
+@property(nonatomic, readonly, strong) WKBackForwardList* backForwardList;
+@property(nonatomic, readonly) BOOL canGoBack;
+@property(nonatomic, readonly) BOOL canGoForward;
+
+- (nullable WKNavigation*)goBack;
+- (nullable WKNavigation*)goForward;
+- (nullable WKNavigation*)goToBackForwardListItem:(WKBackForwardListItem*)item;
+
+@end
+NS_ASSUME_NONNULL_END
+
+#endif  // IOS_WEB_WEB_STATE_UI_WEB_VIEW_NAVIGATION_PROXY_H_