Keep track in the browser of which frames have onunload and onbeforeunload handlers.

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 650 matching lines @@
   void handleAccessibilityFindInPageResult(
       int identifier,
       int match_index,
       const blink::WebAXObject& start_object,
       int start_offset,
       const blink::WebAXObject& end_object,
       int end_offset) override;
   void didChangeManifest() override;
   void enterFullscreen() override;
   void exitFullscreen() override;
+  void suddenTerminationDisablerChanged(
+      bool present,
+      blink::WebFrameClient::SuddenTerminationDisablerType type) override;
   void registerProtocolHandler(const blink::WebString& scheme,
                                const blink::WebURL& url,
                                const blink::WebString& title) override;
   void unregisterProtocolHandler(const blink::WebString& scheme,
                                  const blink::WebURL& url) override;
   void checkIfAudioSinkExistsAndIsAuthorized(
       const blink::WebString& sink_id,
       const blink::WebSecurityOrigin& security_origin,
       blink::WebSetSinkIdCallbacks* web_callbacks) override;
   blink::WebPageVisibilityState visibilityState() const override;
@@ skipping 742 matching lines @@
   std::unique_ptr<PendingNavigationInfo> pending_navigation_info_;
 
   base::WeakPtrFactory<RenderFrameImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_FRAME_IMPL_H_