[crankshaft] Remove the useless HMapEnumLength instruction.

src/crankshaft/arm/lithium-arm.cc

Index: src/crankshaft/arm/lithium-arm.cc
diff --git a/src/crankshaft/arm/lithium-arm.cc b/src/crankshaft/arm/lithium-arm.cc
index 27010cd47481dd9eddcbb8d081208802cc02882c..bf9933d85dfcae62c411d5c1605d7db899dc9759 100644
--- a/src/crankshaft/arm/lithium-arm.cc
+++ b/src/crankshaft/arm/lithium-arm.cc
@@ -1819,12 +1819,6 @@ LInstruction* LChunkBuilder::DoClassOfTestAndBranch(
 }
 
 
-LInstruction* LChunkBuilder::DoMapEnumLength(HMapEnumLength* instr) {
-  LOperand* map = UseRegisterAtStart(instr->value());
-  return DefineAsRegister(new(zone()) LMapEnumLength(map));
-}
-
-
 LInstruction* LChunkBuilder::DoSeqStringGetChar(HSeqStringGetChar* instr) {
   LOperand* string = UseRegisterAtStart(instr->string());
   LOperand* index = UseRegisterOrConstantAtStart(instr->index());