[turbofan] Introduce an ExternalPointer type.

test/unittests/compiler/escape-analysis-unittest.cc

 // Copyright 2015 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/escape-analysis.h"
 #include "src/bit-vector.h"
 #include "src/compiler/escape-analysis-reducer.h"
 #include "src/compiler/graph-visualizer.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/node-properties.h"
@@ skipping 101 matching lines @@
                             control);
   }
 
   Node* Return(Node* value, Node* effect = nullptr, Node* control = nullptr) {
     if (!effect) {
       effect = effect_;
     }
     if (!control) {
       control = control_;
     }
-    Node* zero = graph()->NewNode(common()->Int32Constant(0));
+    Node* zero = graph()->NewNode(common()->NumberConstant(0));
     return control_ = graph()->NewNode(common()->Return(), zero, value, effect,
                                        control);
   }
 
   void EndGraph() {
     for (Edge edge : graph()->end()->input_edges()) {
       if (NodeProperties::IsControlEdge(edge)) {
         edge.UpdateTo(control_);
       }
     }
@@ skipping 377 matching lines @@
   ASSERT_EQ(object1, NodeProperties::GetValueInput(object_state, 0));
   ASSERT_EQ(object_state, NodeProperties::GetValueInput(object_state, 1));
 
   Node* object_state2 = NodeProperties::GetValueInput(state_values1, 0);
   ASSERT_EQ(object_state, object_state2);
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8