[DevTools] Unpause renderer when paused RenderFrame is closed.

content/public/renderer/render_frame_observer.h

Index: content/public/renderer/render_frame_observer.h
diff --git a/content/public/renderer/render_frame_observer.h b/content/public/renderer/render_frame_observer.h
index 161f6c8c3bc9ea12cb99f70c42988feb575182fe..3d06dd5915cec8ccee0099fb6a35f0ec889bd709 100644
--- a/content/public/renderer/render_frame_observer.h
+++ b/content/public/renderer/render_frame_observer.h
@@ -45,6 +45,9 @@ class CONTENT_EXPORT RenderFrameObserver : public IPC::Listener,
   virtual void WasHidden() {}
   virtual void WasShown() {}
 
+  // Called when associated widget is about to close.
+  virtual void WidgetWillClose() {}
+
   // These match the Blink API notifications
   virtual void DidCommitProvisionalLoad(bool is_new_navigation,
                                         bool is_same_page_navigation) {}