chrome: dbus: support asynchronous method replies

dbus/exported_object.h

Index: dbus/exported_object.h
diff --git a/dbus/exported_object.h b/dbus/exported_object.h
index bc67bcdb6e5e3913f5865c579e632c0dfc7f44b6..7ac2f88445dec5695ee14c9e2eed5f5b3400edcf 100644
--- a/dbus/exported_object.h
+++ b/dbus/exported_object.h
@@ -38,9 +38,15 @@ class ExportedObject : public base::RefCountedThreadSafe<ExportedObject> {
                  const std::string& service_name,
                  const std::string& object_path);
 
+  // Called to send a response from an exported method. Response* is the
+  // response message. Callers should pass a NULL Response* in the event
+  // of an error that prevents the sending of a response.
+  typedef base::Callback<void (Response*)> ResponseSender;
+
   // Called when an exported method is called. MethodCall* is the request
-  // message.
-  typedef base::Callback<Response* (MethodCall*)> MethodCallCallback;
+  // message. ResponseSender is the callback that should be used to send a
+  // response.
+  typedef base::Callback<void (MethodCall*, ResponseSender)> MethodCallCallback;
 
   // Called when method exporting is done.
   // Parameters:
@@ -124,7 +130,14 @@ class ExportedObject : public base::RefCountedThreadSafe<ExportedObject> {
                  MethodCall* method_call,
                  base::TimeTicks start_time);
 
-  // Called on completion of the method run from RunMethod().
+  // Callback invoked by service provider to send a response to a method call.
+  // Can be called immediately from a MethodCallCallback to implement a
+  // synchronous service or called later to implement an asynchronous service.
+  void SendResponse(base::TimeTicks start_time,
+                    MethodCall* method_call,
+                    Response* response);
+
+  // Called on completion of the method run from SendResponse().
   // Takes ownership of |method_call| and |response|.
   void OnMethodCompleted(MethodCall* method_call,
                          Response* response,