Refactor lithium classes to reduce the number of virtual functions.

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
===================================================================
--- src/ia32/lithium-ia32.cc	(revision 7679)
+++ src/ia32/lithium-ia32.cc	(working copy)
@@ -43,6 +43,7 @@
 LITHIUM_CONCRETE_INSTRUCTION_LIST(DEFINE_COMPILE)
 #undef DEFINE_COMPILE
 
+
 LOsrEntry::LOsrEntry() {
   for (int i = 0; i < Register::kNumAllocatableRegisters; ++i) {
     register_spills_[i] = NULL;
@@ -449,7 +450,7 @@
 
 
 void LChunk::AddInstruction(LInstruction* instr, HBasicBlock* block) {
-  LGap* gap = new LGap(block);
+  LInstructionGap* gap = new LInstructionGap(block);
   int index = -1;
   if (instr->IsControl()) {
     instructions_.Add(gap);