test_runner: Move more Mock* files into content namespace.

content/shell/renderer/test_runner/MockWebAudioDevice.cpp

 // Copyright 2013 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 "content/shell/renderer/test_runner/MockWebAudioDevice.h"
 
-using namespace blink;
-
-namespace WebTestRunner {
+namespace content {
 
 MockWebAudioDevice::MockWebAudioDevice(double sampleRate)
     : m_sampleRate(sampleRate)
 {
 }
 
 MockWebAudioDevice::~MockWebAudioDevice()
 {
 }
 
 void MockWebAudioDevice::start()
 {
 }
 
 void MockWebAudioDevice::stop()
 {
 }
 
 double MockWebAudioDevice::sampleRate()
 {
     return m_sampleRate;
 }
 
-} // namespace WebTestRunner
+}  // namespace content