diff -r 000000000000 -r 6474c204b198 ipc/chromium/src/base/non_thread_safe.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ipc/chromium/src/base/non_thread_safe.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,52 @@
+// Copyright (c) 2006-2008 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 BASE_NON_THREAD_SAFE_H__
+#define BASE_NON_THREAD_SAFE_H__
+
+#include "base/platform_thread.h"
+
+// A helper class used to help verify that methods of a class are
+// called from the same thread.  One can inherit from this class and use
+// CalledOnValidThread() to verify.
+//
+// This is intended to be used with classes that appear to be thread safe, but
+// aren't.  For example, a service or a singleton like the preferences system.
+//
+// Example:
+// class MyClass : public NonThreadSafe {
+//  public:
+//   void Foo() {
+//     DCHECK(CalledOnValidThread());
+//     ... (do stuff) ...
+//   }
+// }
+//
+// In Release mode, CalledOnValidThread will always return true.
+//
+#ifndef NDEBUG
+class NonThreadSafe {
+ public:
+  NonThreadSafe();
+  ~NonThreadSafe();
+
+  bool CalledOnValidThread() const;
+
+ private:
+  PlatformThreadId valid_thread_id_;
+};
+#else
+// Do nothing in release mode.
+class NonThreadSafe {
+ public:
+  NonThreadSafe() {}
+  ~NonThreadSafe() {}
+
+  bool CalledOnValidThread() const {
+    return true;
+  }
+};
+#endif  // NDEBUG
+
+#endif  // BASE_NON_THREAD_SAFE_H__