[crankshaft] Remove the useless HMapEnumLength instruction.

src/crankshaft/mips64/lithium-codegen-mips64.cc

Index: src/crankshaft/mips64/lithium-codegen-mips64.cc
diff --git a/src/crankshaft/mips64/lithium-codegen-mips64.cc b/src/crankshaft/mips64/lithium-codegen-mips64.cc
index 90207be6b07a5c1e932088ecc66f9a7db139ccf9..a4c38a1c495662a9bceeee37153892e9f983cdbd 100644
--- a/src/crankshaft/mips64/lithium-codegen-mips64.cc
+++ b/src/crankshaft/mips64/lithium-codegen-mips64.cc
@@ -1747,13 +1747,6 @@ void LCodeGen::DoConstantT(LConstantT* instr) {
 }
 
 
-void LCodeGen::DoMapEnumLength(LMapEnumLength* instr) {
-  Register result = ToRegister(instr->result());
-  Register map = ToRegister(instr->value());
-  __ EnumLength(result, map);
-}
-
-
 MemOperand LCodeGen::BuildSeqStringOperand(Register string,
                                            LOperand* index,
                                            String::Encoding encoding) {