[crankshaft] Remove the useless HMapEnumLength instruction.

src/crankshaft/x64/lithium-x64.h

Index: src/crankshaft/x64/lithium-x64.h
diff --git a/src/crankshaft/x64/lithium-x64.h b/src/crankshaft/x64/lithium-x64.h
index ebe1ef9e5dbe7d1f71cce0e98cb9f5e689366943..f9c38b28f25272c8cc2c05be0e9df6ee4b7b52c8 100644
--- a/src/crankshaft/x64/lithium-x64.h
+++ b/src/crankshaft/x64/lithium-x64.h
@@ -101,7 +101,6 @@ class LCodeGen;
   V(LoadKeyedGeneric)                        \
   V(LoadNamedField)                          \
   V(LoadNamedGeneric)                        \
-  V(MapEnumLength)                           \
   V(MathAbs)                                 \
   V(MathClz32)                               \
   V(MathExp)                                 \
@@ -1330,18 +1329,6 @@ class LCmpMapAndBranch final : public LControlInstruction<1, 0> {
 };
 
 
-class LMapEnumLength final : public LTemplateInstruction<1, 1, 0> {
- public:
-  explicit LMapEnumLength(LOperand* value) {
-    inputs_[0] = value;
-  }
-
-  LOperand* value() { return inputs_[0]; }
-
-  DECLARE_CONCRETE_INSTRUCTION(MapEnumLength, "map-enum-length")
-};
-
-
 class LSeqStringGetChar final : public LTemplateInstruction<1, 2, 0> {
  public:
   LSeqStringGetChar(LOperand* string, LOperand* index) {