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

src/ia32/lithium-ia32.h

Index: src/ia32/lithium-ia32.h
diff --git a/src/ia32/lithium-ia32.h b/src/ia32/lithium-ia32.h
index be1940baa3cd79f09bcd88491dc4f227ffa5d6db..83a6c6f32b042df99551db1a616fb64bdc8fd203 100644
--- a/src/ia32/lithium-ia32.h
+++ b/src/ia32/lithium-ia32.h
@@ -126,6 +126,7 @@ class LCodeGen;
   V(LoadNamedField)                             \
   V(LoadNamedFieldPolymorphic)                  \
   V(LoadNamedGeneric)                           \
+  V(MapEnumLength)                              \
   V(MathFloorOfDiv)                             \
   V(MathMinMax)                                 \
   V(MathPowHalf)                                \
@@ -1019,6 +1020,16 @@ class LFixedArrayBaseLength: public LTemplateInstruction<1, 1, 0> {
 };
 
 
+class LMapEnumLength: public LTemplateInstruction<1, 1, 0> {
+ public:
+  explicit LMapEnumLength(LOperand* value) {
+    inputs_[0] = value;
+  }
+
+  DECLARE_CONCRETE_INSTRUCTION(MapEnumLength, "map-enum-length")
+};
+
+
 class LElementsKind: public LTemplateInstruction<1, 1, 0> {
  public:
   explicit LElementsKind(LOperand* value) {