Enable base::NonThreadSafe when DCHECK_ALWAYS_ON is set

base/threading/non_thread_safe.h

Index: base/threading/non_thread_safe.h
diff --git a/base/threading/non_thread_safe.h b/base/threading/non_thread_safe.h
index da7b52815c0aba06d4d4a12001bfa22aa6e11783..de78dfcecbe53417517983183572b51423c791a0 100644
--- a/base/threading/non_thread_safe.h
+++ b/base/threading/non_thread_safe.h
@@ -6,13 +6,28 @@
 #define BASE_THREADING_NON_THREAD_SAFE_H_
 #pragma once
 
-// Classes deriving from NonThreadSafe may need to supress MSVC warning 4275:
+// Classes deriving from NonThreadSafe may need to suppress MSVC warning 4275:
 // non dll-interface class 'Bar' used as base for dll-interface class 'Foo'.
 // There is a specific macro to do it: NON_EXPORTED_BASE(), defined in
 // compiler_specific.h
 #include "base/compiler_specific.h"
 
-#ifndef NDEBUG
+// Apart from debug builds, we also enable the NonThreadSafe checks 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 NonThreadSafe would be
+// disabled) but have DCHECKs enabled at runtime.

[jam, 2012/06/26 01:56:30]

nit: instead of copying the comment, I would just say 
// see comment at top of thread_checker.h

+#if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON))
+#define ENABLE_NON_THREAD_SAFE 1
+#else
+#define ENABLE_NON_THREAD_SAFE 0
+#endif
+
+#if ENABLE_NON_THREAD_SAFE
 #include "base/threading/non_thread_safe_impl.h"
 #endif
 
@@ -53,15 +68,15 @@ class NonThreadSafeDoNothing {
 // to have a base::ThreadChecker as a member, rather than inherit from
 // NonThreadSafe. For more details about when to choose one over the other, see
 // the documentation for base::ThreadChecker.
-//
-// In Release mode, CalledOnValidThread will always return true.
-#ifndef NDEBUG
+#if ENABLE_NON_THREAD_SAFE
 class NonThreadSafe : public NonThreadSafeImpl {
 };
 #else
 class NonThreadSafe : public NonThreadSafeDoNothing {
 };
-#endif  // NDEBUG
+#endif  // ENABLE_NON_THREAD_SAFE
+
+#undef ENABLE_NON_THREAD_SAFE
 
 }  // namespace base