[crankshaft] Remove the useless HMapEnumLength instruction.

src/crankshaft/arm/lithium-arm.h

Index: src/crankshaft/arm/lithium-arm.h
diff --git a/src/crankshaft/arm/lithium-arm.h b/src/crankshaft/arm/lithium-arm.h
index 6329f36fb2e10ce332be1413d00bf2f923723a0f..d3e8b94c013afc0c915baa578591a33c56bf6d7e 100644
--- a/src/crankshaft/arm/lithium-arm.h
+++ b/src/crankshaft/arm/lithium-arm.h
@@ -101,7 +101,6 @@ class LCodeGen;
   V(LoadKeyedGeneric)                        \
   V(LoadNamedField)                          \
   V(LoadNamedGeneric)                        \
-  V(MapEnumLength)                           \
   V(MathAbs)                                 \
   V(MathClz32)                               \
   V(MathExp)                                 \
@@ -1361,18 +1360,6 @@ class LCmpMapAndBranch final : public LControlInstruction<1, 1> {
 };
 
 
-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) {