Add tool to visualize machine code/lithium.

src/hydrogen-representation-changes.cc

Index: src/hydrogen-representation-changes.cc
diff --git a/src/hydrogen-representation-changes.cc b/src/hydrogen-representation-changes.cc
index 960113782f847cb024c42d4184401f1e51f58fab..d0c9b58258b591b6ba9be80fb2619e6ad0562813 100644
--- a/src/hydrogen-representation-changes.cc
+++ b/src/hydrogen-representation-changes.cc
@@ -61,6 +61,11 @@ void HRepresentationChangesPhase::InsertRepresentationChangeForUse(
   if (new_value == NULL) {
     new_value = new(graph()->zone()) HChange(
         value, to, is_truncating_to_smi, is_truncating_to_int);
+    if (use_value->position() != RelocInfo::kNoPosition) {
+      new_value->set_position(use_value->position());
+    } else {
+      ASSERT(!FLAG_emit_opt_code_positions || !graph()->info()->IsOptimizing());
+    }
   }
 
   new_value->InsertBefore(next);