Refactor lithium classes to reduce the number of virtual functions.

src/x64/lithium-codegen-x64.h

 // Copyright 2011 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 84 matching lines @@
   void DoDeferredTaggedToI(LTaggedToI* instr);
   void DoDeferredMathAbsTaggedHeapNumber(LUnaryMathOperation* instr);
   void DoDeferredStackCheck(LGoto* instr);
   void DoDeferredStringCharCodeAt(LStringCharCodeAt* instr);
   void DoDeferredStringCharFromCode(LStringCharFromCode* instr);
   void DoDeferredLInstanceOfKnownGlobal(LInstanceOfKnownGlobal* instr,
                                         Label* map_check);
 
   // Parallel move support.
   void DoParallelMove(LParallelMove* move);
+  void DoGap(LGap* instr);
 
   // Emit frame translation commands for an environment.
   void WriteTranslation(LEnvironment* environment, Translation* translation);
 
   // Declare methods that deal with the individual node types.
 #define DECLARE_DO(type) void Do##type(L##type* node);
   LITHIUM_CONCRETE_INSTRUCTION_LIST(DECLARE_DO)
 #undef DECLARE_DO
 
  private:
@@ skipping 238 matching lines @@
  private:
   LCodeGen* codegen_;
   Label entry_;
   Label exit_;
   Label* external_exit_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_LITHIUM_CODEGEN_X64_H_