[turbofan] JSTypedLowering can just look at the type hints.

test/unittests/compiler/js-typed-lowering-unittest.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/compiler/access-builder.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/js-operator.h"
 #include "src/compiler/js-typed-lowering.h"
 #include "src/compiler/machine-operator.h"
@@ skipping 69 matching lines @@
 
  protected:
   Reduction Reduce(Node* node) {
     MachineOperatorBuilder machine(zone());
     SimplifiedOperatorBuilder simplified(zone());
     JSGraph jsgraph(isolate(), graph(), common(), javascript(), &simplified,
                     &machine);
     // TODO(titzer): mock the GraphReducer here for better unit testing.
     GraphReducer graph_reducer(zone(), graph());
     JSTypedLowering reducer(&graph_reducer, &deps_,
-                            JSTypedLowering::kDeoptimizationEnabled |
-                                JSTypedLowering::kTypeFeedbackEnabled,
-                            &jsgraph, zone());
+                            JSTypedLowering::kDeoptimizationEnabled, &jsgraph,
+                            zone());
     return reducer.Reduce(node);
   }
 
   Handle<JSArrayBuffer> NewArrayBuffer(void* bytes, size_t byte_length) {
     Handle<JSArrayBuffer> buffer = factory()->NewJSArrayBuffer();
     JSArrayBuffer::Setup(buffer, isolate(), true, bytes, byte_length);
     return buffer;
   }
 
   Matcher<Node*> IsIntPtrConstant(intptr_t value) {
@@ skipping 844 matching lines @@
   Node* dummy = graph()->NewNode(javascript()->ToObject(), instanceOf, context,
                                  frame_state, effect, control);
   Reduction r = Reduce(instanceOf);
   ASSERT_FALSE(r.Changed());
   ASSERT_EQ(instanceOf, dummy->InputAt(0));
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8