Use a special EnumLength field to indicate number of valid enum cache values.

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index 457e63789b26e0757f2f34747b9cc86654f738de..645b51c9cc699da58013cace01f1ab9e589a02e6 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -1571,6 +1571,12 @@ LInstruction* LChunkBuilder::DoFixedArrayBaseLength(
 }
 
 
+LInstruction* LChunkBuilder::DoMapEnumLength(HMapEnumLength* instr) {
+  LOperand* map = UseRegisterAtStart(instr->value());
+  return DefineAsRegister(new(zone()) LMapEnumLength(map));
+}
+
+
 LInstruction* LChunkBuilder::DoElementsKind(HElementsKind* instr) {
   LOperand* object = UseRegisterAtStart(instr->value());
   return DefineAsRegister(new(zone()) LElementsKind(object));