[es6] Reintroduce the instanceof operator in the backends.

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 d9ed7c3729f42e74bc67f12e78d2ac068bb0163d..d8ee9cd6aaca2bd10da7f80bc1de98480ad6db81 100644
--- a/src/crankshaft/arm/lithium-arm.cc
+++ b/src/crankshaft/arm/lithium-arm.cc
@@ -934,17 +934,6 @@ LInstruction* LChunkBuilder::DoArgumentsElements(HArgumentsElements* elems) {
 }
 
 
-LInstruction* LChunkBuilder::DoInstanceOf(HInstanceOf* instr) {
-  LOperand* left =
-      UseFixed(instr->left(), InstanceOfDescriptor::LeftRegister());
-  LOperand* right =
-      UseFixed(instr->right(), InstanceOfDescriptor::RightRegister());
-  LOperand* context = UseFixed(instr->context(), cp);
-  LInstanceOf* result = new (zone()) LInstanceOf(context, left, right);
-  return MarkAsCall(DefineFixed(result, r0), instr);
-}
-
-
 LInstruction* LChunkBuilder::DoHasInPrototypeChainAndBranch(
     HHasInPrototypeChainAndBranch* instr) {
   LOperand* object = UseRegister(instr->object());