[Extensions Bindings] Request JS execution from messaging bindings

extensions/renderer/extension_bindings_system.h

 // Copyright 2016 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 EXTENSIONS_RENDERER_EXTENSION_BINDINGS_SYSTEM_H_
 #define EXTENSIONS_RENDERER_EXTENSION_BINDINGS_SYSTEM_H_
 
 #include <string>
 
 namespace base {
@@ skipping 26 matching lines @@
   virtual void UpdateBindingsForContext(ScriptContext* context) = 0;
 
   // Dispatches an event with the given |name|, |event_args|, and
   // |filtering_info| in the given |context|.
   virtual void DispatchEventInContext(
       const std::string& event_name,
       const base::ListValue* event_args,
       const base::DictionaryValue* filtering_info,
       ScriptContext* context) = 0;
 
+  // Returns true if there is a listener for the given |event_name| in the
+  // associated |context|.
+  virtual bool HasEventListenerInContext(const std::string& event_name,
+                                         ScriptContext* context) = 0;
+
   // Handles the response associated with the given |request_id|.
   virtual void HandleResponse(int request_id,
                               bool success,
                               const base::ListValue& response,
                               const std::string& error) = 0;
 
   // Returns the associated RequestSender, if any.
   // TODO(devlin): Factor this out.
   virtual RequestSender* GetRequestSender() = 0;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_RENDERER_EXTENSION_BINDINGS_SYSTEM_H_