Initial UserTag and dart:profiler library

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/bigint_operations.h"
 #include "vm/object.h"
 #include "vm/object_store.h"
 #include "vm/snapshot.h"
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
@@ skipping 2675 matching lines @@
   if (kind == Snapshot::kMessage) {
     // We do not allow objects with native fields in an isolate message.
     writer->SetWriteException(Exceptions::kArgument,
                               "Illegal argument in isolate message"
                               " : (object is a MirrorReference)");
   } else {
     UNREACHABLE();
   }
 }
 
+
+RawUserTag* UserTag::ReadFrom(SnapshotReader* reader,
+                              intptr_t object_id,
+                              intptr_t tags,
+                              Snapshot::Kind kind) {
+  UNREACHABLE();
+  return UserTag::null();
+}
+
+
+void RawUserTag::WriteTo(SnapshotWriter* writer,
+                         intptr_t object_id,
+                         Snapshot::Kind kind) {
+  if (kind == Snapshot::kMessage) {
+    // 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