Enable ThreadChecker in non-debug builds if DCHECK_ALWAYS_ON is

base/threading/thread_checker.h

 // Copyright (c) 2010 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_THREADING_THREAD_CHECKER_H_
 #define BASE_THREADING_THREAD_CHECKER_H_
 #pragma once
 
-#ifndef NDEBUG
+// Apart from debug builds, we also enable the thread checker in
+// builds with DCHECK_ALWAYS_ON so that trybots and waterfall bots
+// with this define will get the same level of thread checking as
+// debug bots.
+//
+// Note that this does not perfectly match situations where DCHECK is
+// enabled.  For example a non-official release build may have
+// DCHECK_ALWAYS_ON undefined (and therefore ThreadChecker would be
+// disabled) but have DCHECKs enabled at runtime.
+#define ENABLE_THREAD_CHECKER (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON))
+
+#if ENABLE_THREAD_CHECKER
 #include "base/threading/thread_checker_impl.h"
 #endif
 
 namespace base {
 
 // Do nothing implementation, for use in release mode.
 //
 // Note: You should almost always use the ThreadChecker class to get the
 // right version for your build configuration.
 class ThreadCheckerDoNothing {
  public:
   bool CalledOnValidThread() const {
     return true;
   }
 
   void DetachFromThread() {}
+
+  static bool IsEnabled() {
+    return false;
+  }
 };
 
 // Before using this class, please consider using NonThreadSafe as it
 // makes it much easier to determine the nature of your class.
 //
 // ThreadChecker is a helper class used to help verify that some methods of a
 // class are called from the same thread.  One can inherit from this class and
 // use CalledOnValidThread() to verify.
 //
 // Inheriting from class indicates that one must be careful when using the
 // class with multiple threads. However, it is up to the class document to
 // indicate how it can be used with threads.
 //
 // Example:
 // class MyClass : public ThreadChecker {
 //  public:
 //   void Foo() {
 //     DCHECK(CalledOnValidThread());
 //     ... (do stuff) ...
 //   }
 // }
 //
 // In Release mode, CalledOnValidThread will always return true.
-#ifndef NDEBUG
+#if ENABLE_THREAD_CHECKER
 class ThreadChecker : public ThreadCheckerImpl {
 };
 #else
 class ThreadChecker : public ThreadCheckerDoNothing {
 };
-#endif  // NDEBUG
+#endif  // ENABLE_THREAD_CHECKER
+
+#undef ENABLE_THREAD_CHECKER
 
 }  // namespace base
 
 #endif  // BASE_THREADING_THREAD_CHECKER_H_