[es6] Reintroduce the instanceof operator in the backends.

src/crankshaft/mips/lithium-mips.cc

Index: src/crankshaft/mips/lithium-mips.cc
diff --git a/src/crankshaft/mips/lithium-mips.cc b/src/crankshaft/mips/lithium-mips.cc
index f9c68e0b18290f1f53548ae56ca07d2c8567e369..345694d78fc3202725ea5bce1e4d1853010e6e63 100644
--- a/src/crankshaft/mips/lithium-mips.cc
+++ b/src/crankshaft/mips/lithium-mips.cc
@@ -939,17 +939,6 @@ 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, v0), instr);
-}
-
-
 LInstruction* LChunkBuilder::DoHasInPrototypeChainAndBranch(
     HHasInPrototypeChainAndBranch* instr) {
   LOperand* object = UseRegister(instr->object());