Fix NavigationHandle being thrown out and recreated (without all the state) after rapid navigations.

content/renderer/render_frame_impl.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 CONTENT_RENDERER_RENDER_FRAME_IMPL_H_
 #define CONTENT_RENDERER_RENDER_FRAME_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 1398 matching lines @@
   service_manager::BindSourceInfo browser_info_;
 
   mojo::BindingSet<service_manager::mojom::InterfaceProvider>
       interface_provider_bindings_;
 
   mojom::URLLoaderFactoryPtr url_loader_factory_;
 
   // AndroidOverlay routing token from the browser, if we have one yet.
   base::Optional<base::UnguessableToken> overlay_routing_token_;
 
+  // PlzNavigate: true after the beforeunload handler that proceeded ran, and
+  // before the next navigation has committed.
+  bool ran_before_unload_ = false;
+
   // Callbacks that we should call when we get a routing token.
   std::vector<media::RoutingTokenCallback> pending_routing_token_callbacks_;
 
   base::WeakPtrFactory<RenderFrameImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_FRAME_IMPL_H_