[crankshaft] Remove the useless HMapEnumLength instruction.

src/crankshaft/mips64/lithium-mips64.h

Index: src/crankshaft/mips64/lithium-mips64.h
diff --git a/src/crankshaft/mips64/lithium-mips64.h b/src/crankshaft/mips64/lithium-mips64.h
index 01dc234c5af6b51788def8288049e3120e5c4bfc..52ba4682182e883f9d1868d6ca491a82df65b97c 100644
--- a/src/crankshaft/mips64/lithium-mips64.h
+++ b/src/crankshaft/mips64/lithium-mips64.h
@@ -103,7 +103,6 @@ class LCodeGen;
   V(LoadKeyedGeneric)                        \
   V(LoadNamedField)                          \
   V(LoadNamedGeneric)                        \
-  V(MapEnumLength)                           \
   V(MathAbs)                                 \
   V(MathExp)                                 \
   V(MathClz32)                               \
@@ -1356,18 +1355,6 @@ 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) {