Create read only handles for empty_array and sentinel objects

vm/symbols.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_SYMBOLS_H_
 #define VM_SYMBOLS_H_
 
 #include "vm/object.h"
 #include "vm/snapshot_ids.h"
 
@@ skipping 206 matching lines @@
 
   // Returns char* of predefined symbol.
   static const char* Name(SymbolId symbol);
 
   static RawString* FromCharCode(int32_t char_code);
 
   static RawString** PredefinedAddress() {
     return reinterpret_cast<RawString**>(&predefined_);
   }
 
-  static bool IsPredefinedHandle(uword address);
-
   static void DumpStats();
 
  private:
   enum {
     kInitialVMIsolateSymtabSize = 512,
     kInitialSymtabSize = 2048
   };
 
   // Helper functions to create a symbol given a string or set of characters.
   template<typename CharacterType, typename CallbackType>
@@ skipping 32 matching lines @@
   }
 
   // List of symbols that are stored in the vm isolate for easy access.
   static RawString* predefined_[kMaxId];
 
   // Statistics used to measure the efficiency of the symbol table.
   static const intptr_t kMaxCollisionBuckets = 10;
   static intptr_t num_of_grows_;
   static intptr_t collision_count_[kMaxCollisionBuckets];
 
-  // Structure for managing handles allocation for symbols that are
-  // stored in the vm isolate. We don't want these handles to be
-  // destroyed as part of the C++ static destructors and hence this
-  // object is dynamically allocated.
-  class ReadOnlyHandles {
-    public:
-      ReadOnlyHandles() { }
-      uword AllocateHandle() {
-        return handles_.AllocateScopedHandle();
-      }
-      bool IsValidHandle(uword address) {
-        return handles_.IsValidScopedHandle(address);
-      }
-
-    private:
-      VMHandles handles_;
-
-      DISALLOW_COPY_AND_ASSIGN(ReadOnlyHandles);
-  };
-  static ReadOnlyHandles* predefined_handles_;
-
 #define DECLARE_SYMBOL_HANDLE(symbol)                                          \
   static String* symbol##_handle_;
 PREDEFINED_SYMBOL_HANDLES_LIST(DECLARE_SYMBOL_HANDLE)
 #undef DECLARE_SYMBOL_HANDLE
 
   friend class String;
   friend class SnapshotReader;
   friend class SnapshotWriter;
   friend class ApiMessageReader;
 
   DISALLOW_COPY_AND_ASSIGN(Symbols);
 };
 
 }  // namespace dart
 
 #endif  // VM_SYMBOLS_H_