Add a version number for full and script snapshots.

runtime/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 254 matching lines @@
   // Reads an object.
   RawObject* ReadObject();
 
   // Add object to backward references.
   void AddBackRef(intptr_t id, Object* obj, DeserializeState state);
 
   // Get an object from the backward references list.
   Object* GetBackRef(intptr_t id);
 
   // Read a full snap shot.
-  void ReadFullSnapshot();
+  RawApiError* ReadFullSnapshot();
+
+  // Read a script snap shot.
+  RawObject* ReadScriptSnapshot();
 
   // Helper functions for creating uninitialized versions
   // of various object types. These are used when reading a
   // full snapshot.
   RawArray* NewArray(intptr_t len);
   RawImmutableArray* NewImmutableArray(intptr_t len);
   RawOneByteString* NewOneByteString(intptr_t len);
   RawTwoByteString* NewTwoByteString(intptr_t len);
   RawTypeArguments* NewTypeArguments(intptr_t len);
   RawTokenStream* NewTokenStream(intptr_t len);
@@ skipping 436 matching lines @@
  private:
   SnapshotWriter* writer_;
   bool as_references_;
 
   DISALLOW_COPY_AND_ASSIGN(SnapshotWriterVisitor);
 };
 
 }  // namespace dart
 
 #endif  // VM_SNAPSHOT_H_