MainFrameObserver is inline owned, so it shouldn't be freed by OnDestruct

content/renderer/web_ui_mojo.h

 // Copyright 2014 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_WEB_UI_MOJO_H_
 #define CONTENT_RENDERER_WEB_UI_MOJO_H_
 
 #include <string>
 
 #include "content/public/renderer/render_frame_observer.h"
@@ skipping 22 matching lines @@
  private:
   class MainFrameObserver : public RenderFrameObserver {
    public:
     explicit MainFrameObserver(WebUIMojo* web_ui_mojo);
     ~MainFrameObserver() override;
 
     // RenderFrameObserver overrides:
     void WillReleaseScriptContext(v8::Local<v8::Context> context,
                                   int world_id) override;
     void DidFinishDocumentLoad() override;
+    // MainFrameObserver is inline owned by WebUIMojo and should not be
+    // destroyed when the main RenderFrame is deleted. Overriding the
+    // OnDestruct method allows this object to remain alive and be cleaned
+    // up as part of WebUIMojo deletion.
+    void OnDestruct() override;
 
    private:
     WebUIMojo* web_ui_mojo_;
 
     DISALLOW_COPY_AND_ASSIGN(MainFrameObserver);
   };
 
   ~WebUIMojo() override;
 
   void CreateContextState();
@@ skipping 10 matching lines @@
   void DidClearWindowObject(blink::WebLocalFrame* frame) override;
 
   MainFrameObserver main_frame_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(WebUIMojo);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_WEB_UI_MOJO_H_