Move symbol table from per isolate snapshot to vm isolate snapshot, this reduces the per isolate in…

runtime/vm/object_store.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_OBJECT_STORE_H_
 #define VM_OBJECT_STORE_H_
 
 #include "vm/object.h"
 
 namespace dart {
@@ skipping 502 matching lines @@
   RawStacktrace* preallocated_stack_trace_;
   RawFunction* lookup_port_handler_;
   RawTypedData* empty_uint32_array_;
   RawFunction* handle_message_function_;
   RawArray* library_load_error_table_;
   RawObject** to() {
     return reinterpret_cast<RawObject**>(&library_load_error_table_);
   }
 
   friend class SnapshotReader;
+  friend class VmIsolateSnapshotReader;
 
   DISALLOW_COPY_AND_ASSIGN(ObjectStore);
 };
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_STORE_H_