Revert 66719 - Reland r65996. Disallows Singletons on non-joinable thread....

base/thread_restrictions.cc

Index: base/thread_restrictions.cc
===================================================================
--- base/thread_restrictions.cc	(revision 66790)
+++ base/thread_restrictions.cc	(working copy)
@@ -18,16 +18,13 @@
 LazyInstance<ThreadLocalBoolean, LeakyLazyInstanceTraits<ThreadLocalBoolean> >
     g_io_disallowed(LINKER_INITIALIZED);
 
-LazyInstance<ThreadLocalBoolean, LeakyLazyInstanceTraits<ThreadLocalBoolean> >
-    g_singleton_disallowed(LINKER_INITIALIZED);
-
 }  // anonymous namespace
 
 // static
 bool ThreadRestrictions::SetIOAllowed(bool allowed) {
-  bool previous_disallowed = g_io_disallowed.Get().Get();
+  bool previous_allowed = g_io_disallowed.Get().Get();
   g_io_disallowed.Get().Set(!allowed);
-  return !previous_disallowed;
+  return !previous_allowed;
 }
 
 // static
@@ -42,22 +39,6 @@
   }
 }
 
-bool ThreadRestrictions::SetSingletonAllowed(bool allowed) {
-  bool previous_disallowed = g_singleton_disallowed.Get().Get();
-  g_singleton_disallowed.Get().Set(!allowed);
-  return !previous_disallowed;
-}
-
-// static
-void ThreadRestrictions::AssertSingletonAllowed() {
-  if (g_singleton_disallowed.Get().Get()) {
-    LOG(FATAL) << "LazyInstance/Singleton is not allowed to be used on this "
-               << "thread.  Most likely it's because this thread is not "
-               << "joinable, so AtExitManager may have deleted the object "
-               << "on shutdown, leading to a potential shutdown crash.";
-  }
-}
-
 }  // namespace base
 
 #endif  // NDEBUG