Make kAllowedToAccessOnNonjoinableThread debug-only.

base/memory/singleton.h

Index: base/memory/singleton.h
diff --git a/base/memory/singleton.h b/base/memory/singleton.h
index 0d4fc8990c443f3b025c37a5937bf232ca4ac14d..355aad0eeb3aa4a3e9e15fbe92001b43ad91796e 100644
--- a/base/memory/singleton.h
+++ b/base/memory/singleton.h
@@ -63,10 +63,12 @@ struct DefaultSingletonTraits {
   // exit. See below for the required call that makes this happen.
   static const bool kRegisterAtExit = true;
 
+#ifndef NDEBUG
   // Set to false to disallow access on a non-joinable thread.  This is
   // different from kRegisterAtExit because StaticMemorySingletonTraits allows
   // access on non-joinable threads, and gracefully handles this.
   static const bool kAllowedToAccessOnNonjoinableThread = false;
+#endif
 };
 
 
@@ -76,7 +78,9 @@ struct DefaultSingletonTraits {
 template<typename Type>
 struct LeakySingletonTraits : public DefaultSingletonTraits<Type> {
   static const bool kRegisterAtExit = false;
+#ifndef NDEBUG
   static const bool kAllowedToAccessOnNonjoinableThread = true;
+#endif
 };