Undo changes to type propagation and canonicalization from my previous CL.

runtime/vm/flow_graph_type_propagator.cc

Index: runtime/vm/flow_graph_type_propagator.cc
===================================================================
--- runtime/vm/flow_graph_type_propagator.cc	(revision 41899)
+++ runtime/vm/flow_graph_type_propagator.cc	(working copy)
@@ -241,11 +241,6 @@
 
 void FlowGraphTypePropagator::VisitValue(Value* value) {
   CompileType* type = TypeOf(value->definition());
-  if (type == value->definition()->Type()) {
-    value->SetReachingType(NULL);
-    return;
-  }
-
   value->SetReachingType(type);
 
   if (FLAG_trace_type_propagation) {
@@ -646,7 +641,7 @@
 
 CompileType* Value::Type() {
   if (reaching_type_ == NULL) {
-    return definition()->Type();
+    reaching_type_ = definition()->Type();
   }
   return reaching_type_;
 }