[compiler] Remove obsolete JSYield operator.

src/compiler/js-generic-lowering.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/js-generic-lowering.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/machine-operator.h"
@@ skipping 662 matching lines @@
       ExternalReference::address_of_pending_message_obj(isolate());
   node->RemoveInput(NodeProperties::FirstContextIndex(node));
   node->InsertInput(zone(), 0, jsgraph()->ExternalConstant(message_address));
   node->InsertInput(zone(), 1, jsgraph()->IntPtrConstant(0));
   StoreRepresentation representation(MachineRepresentation::kTagged,
                                      kNoWriteBarrier);
   NodeProperties::ChangeOp(node, machine()->Store(representation));
 }
 
 
-void JSGenericLowering::LowerJSYield(Node* node) { UNIMPLEMENTED(); }
-
-
 void JSGenericLowering::LowerJSStackCheck(Node* node) {
   Node* effect = NodeProperties::GetEffectInput(node);
   Node* control = NodeProperties::GetControlInput(node);
 
   Node* limit = graph()->NewNode(
       machine()->Load(MachineType::Pointer()),
       jsgraph()->ExternalConstant(
           ExternalReference::address_of_stack_limit(isolate())),
       jsgraph()->IntPtrConstant(0), effect, control);
   Node* pointer = graph()->NewNode(machine()->LoadStackPointer());
@@ skipping 44 matching lines @@
 }
 
 
 MachineOperatorBuilder* JSGenericLowering::machine() const {
   return jsgraph()->machine();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8