Remove the unused HElementsKind instruction.

src/x64/lithium-x64.h

Index: src/x64/lithium-x64.h
diff --git a/src/x64/lithium-x64.h b/src/x64/lithium-x64.h
index 5d85b398cf6f3b4f2a2640770114ac46972dc7c4..6c44d5ccf36118b5a903238814214c6a001bf6ad 100644
--- a/src/x64/lithium-x64.h
+++ b/src/x64/lithium-x64.h
@@ -91,7 +91,6 @@ class LCodeGen;
   V(Drop)                                       \
   V(DummyUse)                                   \
   V(Dummy)                                      \
-  V(ElementsKind)                               \
   V(ForInCacheArray)                            \
   V(ForInPrepareMap)                            \
   V(FunctionLiteral)                            \
@@ -1236,19 +1235,6 @@ class LMapEnumLength V8_FINAL : public LTemplateInstruction<1, 1, 0> {
 };
 
 
-class LElementsKind V8_FINAL : public LTemplateInstruction<1, 1, 0> {
- public:
-  explicit LElementsKind(LOperand* value) {
-    inputs_[0] = value;
-  }
-
-  LOperand* value() { return inputs_[0]; }
-
-  DECLARE_CONCRETE_INSTRUCTION(ElementsKind, "elements-kind")
-  DECLARE_HYDROGEN_ACCESSOR(ElementsKind)
-};
-
-
 class LValueOf V8_FINAL : public LTemplateInstruction<1, 1, 0> {
  public:
   explicit LValueOf(LOperand* value) {