Propagate class ids using existing type propagation framework.

runtime/vm/il_printer.cc

Index: runtime/vm/il_printer.cc
===================================================================
--- runtime/vm/il_printer.cc	(revision 10775)
+++ runtime/vm/il_printer.cc	(working copy)
@@ -436,8 +436,14 @@
     name = AbstractType::Handle(def.PropagatedType()).Name();
     f->Print(" {PT: %s}", name.ToCString());
   }
+  if (def.has_propagated_cid()) {
+    const Class& cls = Class::Handle(
+        Isolate::Current()->class_table()->At(def.propagated_cid()));
+    f->Print(" {PCid: %s}", String::Handle(cls.Name()).ToCString());
+  }
 }
 
+
 void PhiInstr::PrintTo(BufferFormatter* f) const {
   f->Print("    v%d <- phi(", ssa_temp_index());
   for (intptr_t i = 0; i < inputs_.length(); ++i) {