[es6] Reintroduce the instanceof operator in the backends.

src/crankshaft/arm64/lithium-arm64.cc

Index: src/crankshaft/arm64/lithium-arm64.cc
diff --git a/src/crankshaft/arm64/lithium-arm64.cc b/src/crankshaft/arm64/lithium-arm64.cc
index 308929d21006fec2280f68b53b49370c0c054d3d..2154398eed793299dbb7c5ca663f6d368c6fb953 100644
--- a/src/crankshaft/arm64/lithium-arm64.cc
+++ b/src/crankshaft/arm64/lithium-arm64.cc
@@ -1467,17 +1467,6 @@ LInstruction* LChunkBuilder::DoInnerAllocatedObject(
 }
 
 
-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, x0), instr);
-}
-
-
 LInstruction* LChunkBuilder::DoHasInPrototypeChainAndBranch(
     HHasInPrototypeChainAndBranch* instr) {
   LOperand* object = UseRegister(instr->object());