Add complete ElementKind information directly to Map for objects with elements.

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index dad4ef0d6b9e46959d22704df2f135439481e7cc..ea47d45c70a91c045adc73e5f099aa7f15c9334b 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -753,6 +753,12 @@ class MacroAssembler: public Assembler {
   // Always use unsigned comparisons: above and below, not less and greater.
   void CmpInstanceType(Register map, InstanceType type);
 
+  // Check if a map for a JSObject indicates that the object has fast elements.
+  // Jump to the specified label if it does not.
+  void CheckFastElements(Register map,
+                         Label* fail,
+                         Label::Distance distance = Label::kFar);
+
   // Check if the map of an object is equal to a specified map and
   // branch to label if not. Skip the smi check if not required
   // (object is known to be a heap object)