[es6] Reintroduce the instanceof operator in the backends.

src/interface-descriptors.h

Index: src/interface-descriptors.h
diff --git a/src/interface-descriptors.h b/src/interface-descriptors.h
index 4159ed455b27844576170a84d044560f9b857be7..60d872303481bde9fef34da20f4d1b38f90531b3 100644
--- a/src/interface-descriptors.h
+++ b/src/interface-descriptors.h
@@ -21,7 +21,6 @@ class PlatformInterfaceDescriptor;
   V(VectorStoreTransition)                    \
   V(VectorStoreICTrampoline)                  \
   V(VectorStoreIC)                            \
-  V(InstanceOf)                               \
   V(LoadWithVector)                           \
   V(FastArrayPush)                            \
   V(FastNewClosure)                           \
@@ -336,16 +335,6 @@ class VectorStoreTransitionDescriptor : public StoreDescriptor {
 };
 
 
-class InstanceOfDescriptor final : public CallInterfaceDescriptor {
- public:
-  DECLARE_DESCRIPTOR(InstanceOfDescriptor, CallInterfaceDescriptor)
-
-  enum ParameterIndices { kLeftIndex, kRightIndex, kParameterCount };
-  static const Register LeftRegister();
-  static const Register RightRegister();
-};
-
-
 class VectorStoreICTrampolineDescriptor : public StoreDescriptor {
  public:
   DECLARE_DESCRIPTOR_WITH_CUSTOM_FUNCTION_TYPE(