When deduplicating program metadata, try to use objects from the VM isolate.

runtime/vm/clustered_snapshot.h

 // Copyright (c) 2016, 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 RUNTIME_VM_CLUSTERED_SNAPSHOT_H_
 #define RUNTIME_VM_CLUSTERED_SNAPSHOT_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/bitfield.h"
@@ skipping 103 matching lines @@
 class Serializer : public StackResource {
  public:
   Serializer(Thread* thread,
              Snapshot::Kind kind,
              uint8_t** buffer,
              ReAlloc alloc,
              intptr_t initial_size,
              ImageWriter* image_writer_);
   ~Serializer();
 
-  intptr_t WriteVMSnapshot(const Array& symbols, const Array& scripts);
+  intptr_t WriteVMSnapshot(const Array& symbols,
+                           ZoneGrowableArray<Object*>* seed_objects,
+                           ZoneGrowableArray<Code*>* seed_code);
   void WriteIsolateSnapshot(intptr_t num_base_objects,
                             ObjectStore* object_store);
 
   void AddVMIsolateBaseObjects();
 
   void AddBaseObject(RawObject* base_object) {
     AssignRef(base_object);
     num_base_objects_++;
   }
 
@@ skipping 277 matching lines @@
   Thread* thread_;
   Snapshot::Kind kind_;
   uint8_t** vm_snapshot_data_buffer_;
   uint8_t** isolate_snapshot_data_buffer_;
   ReAlloc alloc_;
   intptr_t vm_isolate_snapshot_size_;
   intptr_t isolate_snapshot_size_;
   ForwardList* forward_list_;
   ImageWriter* vm_image_writer_;
   ImageWriter* isolate_image_writer_;
-  Array& token_streams_;
+  ZoneGrowableArray<Object*>* seed_objects_;
+  ZoneGrowableArray<Code*>* seed_code_;
   Array& saved_symbol_table_;
   Array& new_vm_symbol_table_;
 
   // Stats for benchmarking.
   intptr_t clustered_vm_size_;
   intptr_t clustered_isolate_size_;
   intptr_t mapped_data_size_;
   intptr_t mapped_instructions_size_;
 
   DISALLOW_COPY_AND_ASSIGN(FullSnapshotWriter);
@@ skipping 16 matching lines @@
   intptr_t size_;
   const uint8_t* instructions_buffer_;
   const uint8_t* data_buffer_;
 
   DISALLOW_COPY_AND_ASSIGN(FullSnapshotReader);
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_CLUSTERED_SNAPSHOT_H_