Do not try to patch type objects that are already canonical.

runtime/vm/raw_object_snapshot.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/object.h"
 #include "vm/object_store.h"
 #include "vm/snapshot.h"
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
 #include "vm/visitor.h"
@@ skipping 191 matching lines @@
   UNREACHABLE();  // AbstractType is an abstract class.
 }
 
 
 RawType* Type::ReadFrom(SnapshotReader* reader,
                         intptr_t object_id,
                         intptr_t tags,
                         Snapshot::Kind kind) {
   ASSERT(reader != NULL);
 
+  // Determine if the type class of this type is in the full snapshot.
+  bool typeclass_is_in_fullsnapshot = reader->Read<bool>();
+
   // Allocate type object.
   Type& type = Type::ZoneHandle(reader->zone(), NEW_OBJECT(Type));
   bool is_canonical = RawObject::IsCanonical(tags);
-  bool defer_canonicalization = is_canonical && (kind != Snapshot::kFull);
+  bool defer_canonicalization = is_canonical &&
+      (kind != Snapshot::kFull && typeclass_is_in_fullsnapshot);
   reader->AddBackRef(object_id, &type, kIsDeserialized, defer_canonicalization);
 
   // Set all non object fields.
   type.set_token_pos(reader->Read<int32_t>());
   type.set_type_state(reader->Read<int8_t>());
 
   // Set all the object fields.
   // TODO(5411462): Need to assert No GC can happen here, even though
   // allocations may happen.
   intptr_t num_flds = (type.raw()->to() - type.raw()->from());
@@ skipping 24 matching lines @@
          (ptr()->type_state_ == RawType::kFinalizedUninstantiated));
   ASSERT(ptr()->type_class_ != Object::null());
 
   // Write out the serialization header value for this object.
   writer->WriteInlinedObjectHeader(object_id);
 
   // Write out the class and tags information.
   writer->WriteIndexedObject(kTypeCid);
   writer->WriteTags(writer->GetObjectTags(this));
 
+  // Write out typeclass_is_in_fullsnapshot first as this will
+  // help the reader decide on how to canonicalize the type object.
+  intptr_t tags = writer->GetObjectTags(ptr()->type_class_);
+  bool typeclass_is_in_fullsnapshot =
+      (ClassIdTag::decode(tags) == kClassCid) &&
+      Class::IsInFullSnapshot(reinterpret_cast<RawClass*>(ptr()->type_class_));
+  writer->Write<bool>(typeclass_is_in_fullsnapshot);
+
   // Write out all the non object pointer fields.
   writer->Write<int32_t>(ptr()->token_pos_);
   writer->Write<int8_t>(ptr()->type_state_);
 
   // Write out all the object pointer fields. Since we will be canonicalizing
   // the type object when reading it back we should write out all the fields
   // inline and not as references.
   ASSERT(ptr()->type_class_ != Object::null());
   SnapshotWriterVisitor visitor(writer);
   visitor.VisitPointers(from(), to());
@@ skipping 2727 matching lines @@
     // We do not allow objects with native fields in an isolate message.
     writer->SetWriteException(Exceptions::kArgument,
                               "Illegal argument in isolate message"
                               " : (object is a UserTag)");
   } else {
     UNREACHABLE();
   }
 }
 
 }  // namespace dart