Add thread_status_util_debug.cc back

Summary:
Add thread_status_util_debug.cc back as InstrumentedMutex related tests
are using it to produce wait that can be reflected in the counter.

Test Plan:
./perf_context_test
export ROCKSDB_TESTS=MutexWaitStats
./db_test

Reviewers: sdong, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D33525

util/thread_status_util.h

@@ -60,6 +60,12 @@ class ThreadStatusUtil {
 
   static void ResetThreadStatus();
 
+#ifndef NDEBUG
+  static void TEST_SetStateDelay(
+      const ThreadStatus::StateType state, int micro);
+  static void TEST_StateDelay(const ThreadStatus::StateType state);
+#endif
+
  protected:
   // Initialize the thread-local ThreadStatusUpdater when it finds
   // the cached value is nullptr.  Returns true if it has cached

util/thread_status_util_debug.cc

@@ -0,0 +1,31 @@
+// Copyright (c) 2013, Facebook, Inc.  All rights reserved.
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+
+#include <atomic>
+
+#include "rocksdb/env.h"
+#include "util/thread_status_updater.h"
+#include "util/thread_status_util.h"
+
+namespace rocksdb {
+
+#ifndef NDEBUG
+// the delay for debugging purpose.
+static std::atomic<int> states_delay[ThreadStatus::NUM_STATE_TYPES];
+
+void ThreadStatusUtil::TEST_SetStateDelay(
+    const ThreadStatus::StateType state, int micro) {
+  states_delay[state].store(micro, std::memory_order_relaxed);
+}
+
+void ThreadStatusUtil::TEST_StateDelay(
+    const ThreadStatus::StateType state) {
+  Env::Default()->SleepForMicroseconds(
+      states_delay[state].load(std::memory_order_relaxed));
+}
+
+#endif  // !NDEBUG
+
+}  // namespace rocksdb