Implement SequenceChecker, which is a generalization of ThreadChecker

base/test/null_task_runner.h

Index: base/test/null_task_runner.h
diff --git a/base/test/null_task_runner.h b/base/test/null_task_runner.h
new file mode 100644
index 0000000000000000000000000000000000000000..d6390e5202014740a93f3a1edcad45d21246c846
--- /dev/null
+++ b/base/test/null_task_runner.h
@@ -0,0 +1,34 @@
+// Copyright (c) 2012 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 "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/single_thread_task_runner.h"
+
+namespace base {
+
+// Helper class for tests that need to provide an implementation of a
+// *TaskRunner class but don't actually care about tasks being run.
+
+class NullTaskRunner : public base::SingleThreadTaskRunner {
+ public:
+  NullTaskRunner();
+
+  virtual bool PostDelayedTask(const tracked_objects::Location& from_here,
+                               const base::Closure& task,
+                               base::TimeDelta delay) OVERRIDE;
+  virtual bool PostNonNestableDelayedTask(
+      const tracked_objects::Location& from_here,
+      const base::Closure& task,
+      base::TimeDelta delay) OVERRIDE;
+  // Always returns true to avoid triggering DCHECKs.
+  virtual bool RunsTasksOnCurrentThread() const OVERRIDE;
+
+ protected:
+  virtual ~NullTaskRunner();
+
+  DISALLOW_COPY_AND_ASSIGN(NullTaskRunner);
+};
+
+}  // namespace