Use RunLoop, but do not call RunUntilIdle() multiple times

media/midi/midi_manager_usb_unittest.cc

 // Copyright 2014 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.
 
 #include "media/midi/midi_manager_usb.h"
 
 #include <string>
 
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
@@ skipping 161 matching lines @@
     return client_->complete_start_session_;
   }
 
   MidiResult GetInitializationResult() {
     return client_->result_;
   }
 
   void RunCallbackUntilCallbackInvoked(
       bool result, UsbMidiDevice::Devices* devices) {
     factory_->callback_.Run(result, devices);
-    base::RunLoop run_loop;
-    while (!client_->complete_start_session_)
+    while (!client_->complete_start_session_) {
+      base::RunLoop run_loop;
       run_loop.RunUntilIdle();
+    }
   }
 
   scoped_ptr<MidiManagerUsbForTesting> manager_;
   scoped_ptr<FakeMidiManagerClient> client_;
   // Owned by manager_.
   TestUsbMidiDeviceFactory* factory_;
   Logger logger_;
 
  private:
   scoped_ptr<base::MessageLoop> message_loop_;
@@ skipping 153 matching lines @@
             "data = 0x90 0x45 0x7f\n"
             "MidiManagerClient::ReceiveMidiData port_index = 0 "
             "data = 0xf0 0x00 0x01\n"
             "MidiManagerClient::ReceiveMidiData port_index = 0 data = 0xf7\n",
             logger_.TakeLog());
 }
 
 }  // namespace
 
 }  // namespace media