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..b32ead91381f804c6a82ab51a7623c05b3642c89 100644
--- a/src/ia32/lithium-ia32.h
+++ b/src/ia32/lithium-ia32.h
@@ -84,6 +84,7 @@ class LCodeGen;
   V(ConstantI)                                  \
   V(ConstantT)                                  \
   V(Context)                                    \
+  V(DebugBreak)                                 \
   V(DeclareGlobals)                             \
   V(DeleteProperty)                             \
   V(Deoptimize)                                 \
@@ -569,6 +570,12 @@ class LArgumentsElements: public LTemplateInstruction<1, 0, 0> {
 };
 
 
+class LDebugBreak: public LTemplateInstruction<0, 0, 0> {
+ public:
+  DECLARE_CONCRETE_INSTRUCTION(DebugBreak, "break")
+};
+
+
 class LModI: public LTemplateInstruction<1, 2, 1> {
  public:
   LModI(LOperand* left, LOperand* right, LOperand* temp) {