Remove RenderFrameImpl::is_detaching_, since it appears no longer needed.

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 1057 matching lines @@
   // frame tree at the time the pending navigation commits.
   // Frames added by the parent document are created from the renderer process
   // and are immediately inserted in the frame tree.
   // TODO(dcheng): Remove this once we have FrameTreeHandle and can use the
   // Blink Web* layer to check for provisional frames.
   bool in_frame_tree_;
 
   base::WeakPtr<RenderViewImpl> render_view_;
   int routing_id_;
 
-  bool is_detaching_;
-
   // If this frame was created to replace a proxy, this will store the routing
   // id of the proxy to replace at commit-time, at which time it will be
   // cleared.
   // TODO(creis): Remove this after switching to PlzNavigate.
   int proxy_routing_id_;
 
   // Non-null when the RenderFrame is a local root for compositing, input,
   // layout, etc. A local frame is also a local root iff it does not have a
   // parent that is a local frame.
   scoped_refptr<RenderWidget> render_widget_;
@@ skipping 197 matching lines @@
   mojom::FrameHostPtr frame_host_;
 
   base::WeakPtrFactory<RenderFrameImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_FRAME_IMPL_H_