Add some histograms to the D-Bus library:

dbus/exported_object.h

 // Copyright (c) 2011 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 DBUS_EXPORTED_OBJECT_H_
 #define DBUS_EXPORTED_OBJECT_H_
 #pragma once
 
 #include <string>
 #include <map>
 #include <utility>
 
 #include <dbus/dbus.h>
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/platform_thread.h"
+#include "base/time.h"
 
 class MessageLoop;
 
 namespace dbus {
 
 class Bus;
 class MethodCall;
 class Response;
 class Signal;
 
@@ skipping 70 matching lines @@
                             MethodCallCallback method_call_callback,
                             OnExportedCallback exported_callback);
 
   // Called when the object is exported.
   void OnExported(OnExportedCallback on_exported_callback,
                   const std::string& interface_name,
                   const std::string& method_name,
                   bool success);
 
   // Helper function for SendSignal().
-  void SendSignalInternal(void* signal_message);
+  void SendSignalInternal(base::TimeTicks start_time,
+                          void* signal_message);
 
   // Registers this object to the bus.
   // Returns true on success, or the object is already registered.
   //
   // BLOCKING CALL.
   bool Register();
 
   // Handles the incoming request messages and dispatches to the exported
   // methods.
   DBusHandlerResult HandleMessage(DBusConnection* connection,
@@ skipping 24 matching lines @@
 
   // The method table where keys are absolute method names (i.e. interface
   // name + method name), and values are the corresponding callbacks.
   typedef std::map<std::string, MethodCallCallback> MethodTable;
   MethodTable method_table_;
 };
 
 }  // namespace dbus
 
 #endif  // DBUS_EXPORTED_OBJECT_H_