Refactor Hydrogen GVN into an HPhase and use the phase zone.

src/hydrogen.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 266 matching lines @@
   HEnvironment* start_environment() const { return start_environment_; }
 
   void FinalizeUniqueValueIds();
   void InitializeInferredTypes();
   void InsertTypeConversions();
   void MergeRemovableSimulates();
   void InsertRepresentationChanges();
   void MarkDeoptimizeOnUndefined();
   void ComputeMinusZeroChecks();
   void ComputeSafeUint32Operations();
-  void GlobalValueNumbering();
   bool ProcessArgumentsObject();
   void EliminateRedundantPhis();
   void Canonicalize();
   void OrderBlocks();
   void AssignDominators();
   void SetupInformativeDefinitions();
   void EliminateRedundantBoundsChecks();
   void DehoistSimpleArrayIndexComputations();
   void RestoreActualValues();
   void DeadCodeElimination(const char *phase_name);
@@ skipping 1657 matching lines @@
 };
 
 
 class HPhase : public CompilationPhase {
  public:
   HPhase(const char* name, HGraph* graph)
       : CompilationPhase(name, graph->info()),
         graph_(graph) { }
   ~HPhase();
 
+ protected:
+  HGraph* graph() const { return graph_; }
+
  private:
   HGraph* graph_;
 
   DISALLOW_COPY_AND_ASSIGN(HPhase);
 };
 
 
 class HTracer: public Malloced {
  public:
   explicit HTracer(int isolate_id)
@@ skipping 72 matching lines @@
   EmbeddedVector<char, 64> filename_;
   HeapStringAllocator string_allocator_;
   StringStream trace_;
   int indent_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_H_