Remove recently introduced FunctionType vm class by merging it into class Type.

runtime/vm/raw_object.cc

Index: runtime/vm/raw_object.cc
diff --git a/runtime/vm/raw_object.cc b/runtime/vm/raw_object.cc
index d32b5abf8771f8d5bc1f9cb28092409c0f17534c..307139a047a02642ca2ed5f9f9fffb19b595ec62 100644
--- a/runtime/vm/raw_object.cc
+++ b/runtime/vm/raw_object.cc
@@ -343,13 +343,6 @@ intptr_t RawType::VisitTypePointers(
 }
 
 
-intptr_t RawFunctionType::VisitFunctionTypePointers(
-    RawFunctionType* raw_obj, ObjectPointerVisitor* visitor) {
-  visitor->VisitPointers(raw_obj->from(), raw_obj->to());
-  return FunctionType::InstanceSize();
-}
-
-
 intptr_t RawTypeRef::VisitTypeRefPointers(
     RawTypeRef* raw_obj, ObjectPointerVisitor* visitor) {
   visitor->VisitPointers(raw_obj->from(), raw_obj->to());