[turbofan] Enforce native context specialization.

test/unittests/compiler/js-create-lowering-unittest.cc

 // Copyright 2016 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-create-lowering.h"
 #include "src/code-factory.h"
 #include "src/compilation-dependencies.h"
 #include "src/compiler/access-builder.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/js-operator.h"
@@ skipping 22 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());
     JSCreateLowering reducer(&graph_reducer, &deps_, &jsgraph,
-                             MaybeHandle<LiteralsArray>(),
-                             MaybeHandle<Context>(), zone());
+                             MaybeHandle<LiteralsArray>(), native_context(),
+                             zone());
     return reducer.Reduce(node);
   }
 
   Node* FrameState(Handle<SharedFunctionInfo> shared, Node* outer_frame_state) {
     Node* state_values = graph()->NewNode(common()->StateValues(0));
     return graph()->NewNode(
         common()->FrameState(
             BailoutId::None(), OutputFrameStateCombine::Ignore(),
             common()->CreateFrameStateFunctionInfo(
                 FrameStateType::kJavaScriptFunction, 1, 0, shared)),
@@ skipping 155 matching lines @@
   EXPECT_THAT(r.replacement(),
               IsFinishRegion(IsAllocate(IsNumberConstant(Context::SizeFor(
                                             Context::MIN_CONTEXT_SLOTS + 1)),
                                         IsBeginRegion(_), control),
                              _));
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8