Add a HBreak instruction for debugging

src/ia32/lithium-ia32.h

Index: src/ia32/lithium-ia32.h
diff --git a/src/ia32/lithium-ia32.h b/src/ia32/lithium-ia32.h
index 5df68835f38b4fd23c31355d5e04a674ac0ef706..dde8016b1f807a2aa9defcf0aaf4caa705303643 100644
--- a/src/ia32/lithium-ia32.h
+++ b/src/ia32/lithium-ia32.h
@@ -54,6 +54,7 @@ class LCodeGen;
   V(BitNotI)                                    \
   V(BoundsCheck)                                \
   V(Branch)                                     \
+  V(Break)                                      \
   V(CallConstantFunction)                       \
   V(CallFunction)                               \
   V(CallGlobal)                                 \
@@ -569,6 +570,12 @@ class LArgumentsElements: public LTemplateInstruction<1, 0, 0> {
 };
 
 
+class LBreak: public LTemplateInstruction<0, 0, 0> {
+ public:
+  DECLARE_CONCRETE_INSTRUCTION(Break, "break")
+};
+
+
 class LModI: public LTemplateInstruction<1, 2, 1> {
  public:
   LModI(LOperand* left, LOperand* right, LOperand* temp) {