Some cleanup and be more conservative when guessing cids: use only current leaf classes; otherwise …

runtime/vm/flow_graph_type_propagator.cc

Index: runtime/vm/flow_graph_type_propagator.cc
diff --git a/runtime/vm/flow_graph_type_propagator.cc b/runtime/vm/flow_graph_type_propagator.cc
index f1ec8baed191d07189ed34958bd8831f82e667eb..f22c50f2dd8a72a69d81374b73d30a75cbc2f372 100644
--- a/runtime/vm/flow_graph_type_propagator.cc
+++ b/runtime/vm/flow_graph_type_propagator.cc
@@ -543,8 +543,8 @@ intptr_t CompileType::ToNullableCid() {
       // Don't infer a cid from an abstract type for signature classes since
       // there can be multiple compatible classes with different cids.
       if (!type_class.IsSignatureClass() &&
-          !cha->IsImplemented(type_class) &&
-          !cha->HasSubclasses(type_class)) {
+          !CHA::IsImplemented(type_class) &&
+          !CHA::HasSubclasses(type_class)) {
         if (type_class.IsPrivate()) {
           // Type of a private class cannot change through later loaded libs.
           cid_ = type_class.id();
@@ -780,7 +780,7 @@ CompileType ParameterInstr::ComputeType() const {
     if (type.HasResolvedTypeClass()) {
       Thread* thread = Thread::Current();
       const Class& type_class = Class::Handle(type.type_class());
-      if (!thread->cha()->HasSubclasses(type_class)) {
+      if (!CHA::HasSubclasses(type_class)) {
         if (type_class.IsPrivate()) {
           // Private classes can never be subclassed by later loaded libs.
           cid = type_class.id();