[turbofan] Add TraversalState and GraphTraversal and use them in GraphReducer.

src/compiler/graph-reducer.h

 // 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.
 
 #ifndef V8_COMPILER_GRAPH_REDUCER_H_
 #define V8_COMPILER_GRAPH_REDUCER_H_
 
+#include "src/compiler/graph.h"
 #include "src/zone-containers.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
-// Forward declarations.
-class Graph;
-class Node;
-
-
 // Represents the result of trying to reduce a node in the graph.
 class Reduction FINAL {
  public:
   explicit Reduction(Node* replacement = NULL) : replacement_(replacement) {}
 
   Node* replacement() const { return replacement_; }
   bool Changed() const { return replacement() != NULL; }
 
  private:
   Node* replacement_;
@@ skipping 44 matching lines @@
     int input_index;
   };
 
   // Reduce a single node.
   Reduction Reduce(Node* const);
   // Reduce the node on top of the stack.
   void ReduceTop();
 
   // Node stack operations.
   void Pop();
-  void Push(Node* const);
+  void Push(Node* node);
 
   // Revisit queue operations.
-  bool Recurse(Node* const);
-  void Revisit(Node* const);
+  bool Recurse(Node* node);
+  void Revisit(Node* node);
 
   Graph* graph_;
+  NodeMarker<State> state_;
   ZoneVector<Reducer*> reducers_;
   ZoneStack<Node*> revisit_;
   ZoneStack<NodeState> stack_;
-  ZoneDeque<State> state_;
 
   DISALLOW_COPY_AND_ASSIGN(GraphReducer);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_GRAPH_REDUCER_H_