Refactor lithium classes to reduce the number of virtual functions.

src/ia32/lithium-codegen-ia32.h

Index: src/ia32/lithium-codegen-ia32.h
===================================================================
--- src/ia32/lithium-codegen-ia32.h	(revision 7679)
+++ src/ia32/lithium-codegen-ia32.h	(working copy)
@@ -105,14 +105,15 @@
 
   // Parallel move support.
   void DoParallelMove(LParallelMove* move);
+  void DoGap(LGap* instr);
 
   // Emit frame translation commands for an environment.
   void WriteTranslation(LEnvironment* environment, Translation* translation);
 
   void EnsureRelocSpaceForDeoptimization();
 
-  // Declare methods that deal with the individual node types.
-#define DECLARE_DO(type) void Do##type(L##type* node);
+  // Declare methods that deal with the individual instructions.
+#define DECLARE_DO(type) void Do##type(L##type* instr);
   LITHIUM_CONCRETE_INSTRUCTION_LIST(DECLARE_DO)
 #undef DECLARE_DO