[es6] Reintroduce the instanceof operator in the backends.

src/crankshaft/x64/lithium-x64.h

Index: src/crankshaft/x64/lithium-x64.h
diff --git a/src/crankshaft/x64/lithium-x64.h b/src/crankshaft/x64/lithium-x64.h
index f89c51dd0aeb1ef84c62c50e91e4d013f52a574a..91f554137ac9d17c4e36f01ee74babfdfdadea7e 100644
--- a/src/crankshaft/x64/lithium-x64.h
+++ b/src/crankshaft/x64/lithium-x64.h
@@ -79,7 +79,6 @@ class LCodeGen;
   V(HasInPrototypeChainAndBranch)            \
   V(HasInstanceTypeAndBranch)                \
   V(InnerAllocatedObject)                    \
-  V(InstanceOf)                              \
   V(InstructionGap)                          \
   V(Integer32ToDouble)                       \
   V(InvokeFunction)                          \
@@ -1137,22 +1136,6 @@ class LCmpT final : public LTemplateInstruction<1, 3, 0> {
 };
 
 
-class LInstanceOf final : public LTemplateInstruction<1, 3, 0> {
- public:
-  LInstanceOf(LOperand* context, LOperand* left, LOperand* right) {
-    inputs_[0] = context;
-    inputs_[1] = left;
-    inputs_[2] = right;
-  }
-
-  LOperand* context() { return inputs_[0]; }
-  LOperand* left() { return inputs_[1]; }
-  LOperand* right() { return inputs_[2]; }
-
-  DECLARE_CONCRETE_INSTRUCTION(InstanceOf, "instance-of")
-};
-
-
 class LHasInPrototypeChainAndBranch final : public LControlInstruction<2, 0> {
  public:
   LHasInPrototypeChainAndBranch(LOperand* object, LOperand* prototype) {