Improve and simplify removal of unreachable code

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 d81dc0f57cde1ea708f7a582e3d2fb830571752a..8007dcf35ca40d3d6c288ef3b17c0e2ae23fa706 100644
--- a/src/arm/lithium-arm.h
+++ b/src/arm/lithium-arm.h
@@ -2610,6 +2610,11 @@ class LChunkBuilder BASE_EMBEDDED {
   // Build the sequence for the graph.
   LPlatformChunk* Build();
 
+  LInstruction* ElideControlInstruction(HControlInstruction* instr,
+                                        bool condition);
+
+  void PropagateUnreachableBlockMarks();
+
   // Declare methods that deal with the individual node types.
 #define DECLARE_DO(type) LInstruction* Do##type(H##type* node);
   HYDROGEN_CONCRETE_INSTRUCTION_LIST(DECLARE_DO)