[es6] Reintroduce the instanceof operator in the backends.

src/crankshaft/mips/lithium-codegen-mips.cc

Index: src/crankshaft/mips/lithium-codegen-mips.cc
diff --git a/src/crankshaft/mips/lithium-codegen-mips.cc b/src/crankshaft/mips/lithium-codegen-mips.cc
index 4cadfd03f8f866eed7946d2278b7ed16e726bf6e..79abcda9600383f618db568154197bc8daea20fa 100644
--- a/src/crankshaft/mips/lithium-codegen-mips.cc
+++ b/src/crankshaft/mips/lithium-codegen-mips.cc
@@ -2381,16 +2381,6 @@ void LCodeGen::DoCmpMapAndBranch(LCmpMapAndBranch* instr) {
 }
 
 
-void LCodeGen::DoInstanceOf(LInstanceOf* instr) {
-  DCHECK(ToRegister(instr->context()).is(cp));
-  DCHECK(ToRegister(instr->left()).is(InstanceOfDescriptor::LeftRegister()));
-  DCHECK(ToRegister(instr->right()).is(InstanceOfDescriptor::RightRegister()));
-  DCHECK(ToRegister(instr->result()).is(v0));
-  InstanceOfStub stub(isolate());
-  CallCode(stub.GetCode(), RelocInfo::CODE_TARGET, instr);
-}
-
-
 void LCodeGen::DoHasInPrototypeChainAndBranch(
     LHasInPrototypeChainAndBranch* instr) {
   Register const object = ToRegister(instr->object());