Improve and simplify removal of unreachable code

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 7ae87a08c8dd72c377475eb2d50332f18699b90b..eed1398d284118f5750f24f5cbef3ef19d1ca482 100644
--- a/src/ia32/lithium-ia32.h
+++ b/src/ia32/lithium-ia32.h
@@ -2744,6 +2744,11 @@ 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)