<webview>: Cleanup WebRequest event listeners when embedder destroyed

content/public/browser/browser_plugin_guest_delegate.h

Index: content/public/browser/browser_plugin_guest_delegate.h
diff --git a/content/public/browser/browser_plugin_guest_delegate.h b/content/public/browser/browser_plugin_guest_delegate.h
index 52ebc304a0dec49d635580776348023d2581ebc1..2acaff20c51998e6cf84f7654194b3544e500c20 100644
--- a/content/public/browser/browser_plugin_guest_delegate.h
+++ b/content/public/browser/browser_plugin_guest_delegate.h
@@ -39,6 +39,9 @@ class CONTENT_EXPORT BrowserPluginGuestDelegate {
   // gracefully.
   virtual void GuestProcessGone(base::TerminationStatus status) {}
 
+  // Informs the delegate that the embedder has been destroyed.
+  virtual void EmbedderDestroyed() {}
+
   virtual bool HandleKeyboardEvent(const NativeWebKeyboardEvent& event);
 
   // Notification that a load in the guest resulted in abort. Note that |url|