Add a HBreak instruction for debugging

src/arm/lithium-arm.h

Index: src/arm/lithium-arm.h
diff --git a/src/arm/lithium-arm.h b/src/arm/lithium-arm.h
index 9deed587e3fb9b7bf51f252fb2effbbd0bf78a5c..9bcd44ae05e1e8557e2280c2e4e760cff92f7c44 100644
--- a/src/arm/lithium-arm.h
+++ b/src/arm/lithium-arm.h
@@ -89,6 +89,7 @@ class LCodeGen;
   V(ConstantI)                                  \
   V(ConstantT)                                  \
   V(Context)                                    \
+  V(DebugBreak)                                 \
   V(DeclareGlobals)                             \
   V(DeleteProperty)                             \
   V(Deoptimize)                                 \
@@ -695,6 +696,12 @@ class LMultiplySubD: public LTemplateInstruction<1, 3, 0> {
 };
 
 
+class LDebugBreak: public LTemplateInstruction<0, 0, 0> {
+ public:
+  DECLARE_CONCRETE_INSTRUCTION(DebugBreak, "break")
+};
+
+
 class LCmpIDAndBranch: public LControlInstruction<2, 0> {
  public:
   LCmpIDAndBranch(LOperand* left, LOperand* right) {