--- a/mfbt/Attributes.h
+++ b/mfbt/Attributes.h
@@ -571,16 +571,24 @@
  * MOZ_STATIC_CLASS: Applies to all classes. Any class with this annotation is
  *   expected to live in static memory, so it is a compile-time error to use
  *   it, or an array of such objects, as the type of a variable declaration, or
  *   as a temporary object, or as the type of a new expression (unless
  *   placement new is being used). If a member of another class uses this
  *   class, or if another class inherits from this class, then it is considered
  *   to be a static class as well, although this attribute need not be provided
  *   in such cases.
+ * MOZ_STATIC_LOCAL_CLASS: Applies to all classes. Any class with this
+ *   annotation is expected to be a static local variable, so it is
+ *   a compile-time error to use it, or an array of such objects, or as a
+ *   temporary object, or as the type of a new expression. If another class
+ *   inherits from this class then it is considered to be a static local
+ *   class as well, although this attribute need not be provided in such cases.
+ *   It is also a compile-time error for any class with this annotation to have
+ *   a non-trivial destructor.
  * MOZ_STACK_CLASS: Applies to all classes. Any class with this annotation is
  *   expected to live on the stack, so it is a compile-time error to use it, or
  *   an array of such objects, as a global or static variable, or as the type of
  *   a new expression (unless placement new is being used). If a member of
  *   another class uses this class, or if another class inherits from this
  *   class, then it is considered to be a stack class as well, although this
  *   attribute need not be provided in such cases.
  * MOZ_NONHEAP_CLASS: Applies to all classes. Any class with this annotation is
@@ -761,16 +769,19 @@
 #  if defined(MOZ_CLANG_PLUGIN) || defined(XGILL_PLUGIN)
 #    define MOZ_CAN_RUN_SCRIPT __attribute__((annotate("moz_can_run_script")))
 #    define MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION \
       __attribute__((annotate("moz_can_run_script")))
 #    define MOZ_CAN_RUN_SCRIPT_BOUNDARY \
       __attribute__((annotate("moz_can_run_script_boundary")))
 #    define MOZ_MUST_OVERRIDE __attribute__((annotate("moz_must_override")))
 #    define MOZ_STATIC_CLASS __attribute__((annotate("moz_global_class")))
+#    define MOZ_STATIC_LOCAL_CLASS                        \
+      __attribute__((annotate("moz_static_local_class"))) \
+          __attribute__((annotate("moz_trivial_dtor")))
 #    define MOZ_STACK_CLASS __attribute__((annotate("moz_stack_class")))
 #    define MOZ_NONHEAP_CLASS __attribute__((annotate("moz_nonheap_class")))
 #    define MOZ_HEAP_CLASS __attribute__((annotate("moz_heap_class")))
 #    define MOZ_NON_TEMPORARY_CLASS \
       __attribute__((annotate("moz_non_temporary_class")))
 #    define MOZ_TEMPORARY_CLASS __attribute__((annotate("moz_temporary_class")))
 #    define MOZ_TRIVIAL_CTOR_DTOR \
       __attribute__((annotate("moz_trivial_ctor_dtor")))
@@ -831,16 +842,17 @@
 #      define MOZ_HEAP_ALLOCATOR __attribute__((annotate("moz_heap_allocator")))
 #    endif
 #  else
 #    define MOZ_CAN_RUN_SCRIPT                              /* nothing */
 #    define MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION               /* nothing */
 #    define MOZ_CAN_RUN_SCRIPT_BOUNDARY                     /* nothing */
 #    define MOZ_MUST_OVERRIDE                               /* nothing */
 #    define MOZ_STATIC_CLASS                                /* nothing */
+#    define MOZ_STATIC_LOCAL_CLASS                          /* nothing */
 #    define MOZ_STACK_CLASS                                 /* nothing */
 #    define MOZ_NONHEAP_CLASS                               /* nothing */
 #    define MOZ_HEAP_CLASS                                  /* nothing */
 #    define MOZ_NON_TEMPORARY_CLASS                         /* nothing */
 #    define MOZ_TEMPORARY_CLASS                             /* nothing */
 #    define MOZ_TRIVIAL_CTOR_DTOR                           /* nothing */
 #    define MOZ_ALLOW_TEMPORARY                             /* nothing */
 #    define MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS      /* nothing */