--- a/mfbt/Attributes.h
+++ b/mfbt/Attributes.h
@@ -502,16 +502,24 @@
  *   MOZ_CAN_RUN_SCRIPT. This is important for some bindings and low level code
  *   which need to opt out of the safety checks performed by MOZ_CAN_RUN_SCRIPT.
  * MOZ_MUST_OVERRIDE: Applies to all C++ member functions. All immediate
  *   subclasses must provide an exact override of this method; if a subclass
  *   does not override this method, the compiler will emit an error. This
  *   attribute is not limited to virtual methods, so if it is applied to a
  *   nonvirtual method and the subclass does not provide an equivalent
  *   definition, the compiler will emit an error.
+ * 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_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
@@ -661,16 +669,17 @@
  * MOZ_MAY_CALL_AFTER_MUST_RETURN: Applies to function or method declarations.
  *   Calls to these methods may be made in functions after calls a
  *   MOZ_MUST_RETURN_FROM_CALLER function or method.
  */
 #ifdef MOZ_CLANG_PLUGIN
 #  define MOZ_CAN_RUN_SCRIPT __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_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")))
 #  ifdef DEBUG
      /* in debug builds, these classes do have non-trivial constructors. */
@@ -718,16 +727,17 @@
     _Pragma("clang diagnostic push") \
     _Pragma("clang diagnostic ignored \"-Wgcc-compat\"") \
     __attribute__((annotate("moz_heap_allocator"))) \
     _Pragma("clang diagnostic pop")
 #else
 #  define MOZ_CAN_RUN_SCRIPT /* nothing */
 #  define MOZ_CAN_RUN_SCRIPT_BOUNDARY /* nothing */
 #  define MOZ_MUST_OVERRIDE /* nothing */
+#  define MOZ_STATIC_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_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS /* nothing */
 #  define MOZ_IMPLICIT /* nothing */