test_runner: Move three Mock* files into content namespace.

content/shell/renderer/test_runner/MockConstraints.h

 // 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.
 
 #ifndef CONTENT_SHELL_RENDERER_TEST_RUNNER_MOCKCONSTRAINTS_H_
 #define CONTENT_SHELL_RENDERER_TEST_RUNNER_MOCKCONSTRAINTS_H_
 
 namespace blink {
 class WebMediaConstraints;
 class WebString;
 }
 
-namespace WebTestRunner {
+namespace content {
 
 class MockConstraints {
 public:
     static bool verifyConstraints(const blink::WebMediaConstraints&, blink::WebString* failedConstraint = 0);
 };
 
-}
+}  // content
 
 #endif  // CONTENT_SHELL_RENDERER_TEST_RUNNER_MOCKCONSTRAINTS_H_