Refactor snapshot writing code in preparation for the change to remove recursive calls to WriteObje…

vm/snapshot.h

 // 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.
 
 #ifndef VM_SNAPSHOT_H_
 #define VM_SNAPSHOT_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/bitfield.h"
@@ skipping 504 matching lines @@
     RawObject* raw() const { return raw_; }
     uword tags() const { return tags_; }
 
    private:
     RawObject* raw_;
     uword tags_;
 
     DISALLOW_COPY_AND_ASSIGN(ForwardObjectNode);
   };
 
-  intptr_t MarkObject(RawObject* raw, RawClass* cls);
+  intptr_t MarkObject(RawObject* raw);
+
+  bool CheckAndWritePredefinedObject(RawObject* raw);
 
   void WriteInlinedObject(RawObject* raw);
 
   ObjectStore* object_store() const { return object_store_; }
 
   Snapshot::Kind kind_;
   ObjectStore* object_store_;  // Object store for common classes.
   ClassTable* class_table_;  // Class table for the class index to class lookup.
   GrowableArray<ForwardObjectNode*> forward_list_;
 
@@ skipping 28 matching lines @@
 
  private:
   SnapshotWriter* writer_;
 
   DISALLOW_COPY_AND_ASSIGN(SnapshotWriterVisitor);
 };
 
 }  // namespace dart
 
 #endif  // VM_SNAPSHOT_H_