Remove the unused HElementsKind instruction.

src/mips/lithium-mips.cc

Index: src/mips/lithium-mips.cc
diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index ee64f8ee030f4605d431240c0e992f0731cb4724..374214a7646acee032eb4baf84f1153bd18fd0bf 100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -1633,12 +1633,6 @@ LInstruction* LChunkBuilder::DoMapEnumLength(HMapEnumLength* instr) {
 }
 
 
-LInstruction* LChunkBuilder::DoElementsKind(HElementsKind* instr) {
-  LOperand* object = UseRegisterAtStart(instr->value());
-  return DefineAsRegister(new(zone()) LElementsKind(object));
-}
-
-
 LInstruction* LChunkBuilder::DoValueOf(HValueOf* instr) {
   LOperand* object = UseRegister(instr->value());
   LValueOf* result = new(zone()) LValueOf(object, TempRegister());