--- a/dom/base/nsINode.h
+++ b/dom/base/nsINode.h
@@ -209,16 +209,21 @@ enum {
   //
   // FIXME(bholley): These should move to Element, and we only need one now.
   NODE_SHARED_RESTYLE_BIT_1 =             NODE_FLAG_BIT(21),
   NODE_SHARED_RESTYLE_BIT_2 =             NODE_FLAG_BIT(22),
 
   // Whether this node has dirty descendants for Servo's style system.
   NODE_HAS_DIRTY_DESCENDANTS_FOR_SERVO =  NODE_SHARED_RESTYLE_BIT_1,
 
+  // Whether this node has dirty descendants for animation-only restyle for
+  // Servo's style system.
+  NODE_HAS_ANIMATION_ONLY_DIRTY_DESCENDANTS_FOR_SERVO =
+    NODE_SHARED_RESTYLE_BIT_2,
+
   // Remaining bits are node type specific.
   NODE_TYPE_SPECIFIC_BITS_OFFSET =        23
 };
 
 // Make sure we have space for our bits
 #define ASSERT_NODE_FLAGS_SPACE(n) \
   static_assert(WRAPPER_CACHE_FLAGS_BITS_USED + (n) <=                          \
                   sizeof(nsWrapperCache::FlagsType) * 8,                        \