[compiler] Delete extra map check in StringIterator.

test/unittests/compiler/js-builtin-reducer-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/compiler/js-builtin-reducer.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/node-properties.h"
 #include "src/compiler/simplified-operator.h"
 #include "src/compiler/typer.h"
 #include "src/isolate-inl.h"
@@ skipping 15 matching lines @@
  protected:
   Reduction Reduce(Node* node, MachineOperatorBuilder::Flags flags =
                                    MachineOperatorBuilder::Flag::kNoFlags) {
     MachineOperatorBuilder machine(zone(), MachineType::PointerRepresentation(),
                                    flags);
     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());
+
     JSBuiltinReducer reducer(&graph_reducer, &jsgraph,
-                             JSBuiltinReducer::kNoFlags, nullptr);
+                             JSBuiltinReducer::kNoFlags, nullptr,
+                             native_context());
     return reducer.Reduce(node);
   }
 
   Node* GlobalFunction(const char* name) {
     Handle<JSFunction> f = Handle<JSFunction>::cast(
         Object::GetProperty(
             isolate()->global_object(),
             isolate()->factory()->NewStringFromAsciiChecked(name))
             .ToHandleChecked());
     return HeapConstant(f);
@@ skipping 1529 matching lines @@
   Reduction r = Reduce(call);
 
   ASSERT_TRUE(r.Changed());
   EXPECT_THAT(r.replacement(),
               IsStringFromCharCode(IsPlainPrimitiveToNumber(p0)));
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8