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

src/compiler.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 608 matching lines @@
 
 class CompilationPhase BASE_EMBEDDED {
  public:
   CompilationPhase(const char* name, CompilationInfo* info);
   ~CompilationPhase();
 
  protected:
   bool ShouldProduceTraceOutput() const;
 
   const char* name() const { return name_; }
-  Isolate* isolate() const { return info_->isolate(); }
+  CompilationInfo* info() const { return info_; }
+  Isolate* isolate() const { return info()->isolate(); }
   Zone* zone() { return &zone_; }
 
  private:
   const char* name_;
   CompilationInfo* info_;
   Zone zone_;
   unsigned info_zone_start_allocation_size_;
   int64_t start_ticks_;
 
   DISALLOW_COPY_AND_ASSIGN(CompilationPhase);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_COMPILER_H_