Reimplement Symbols using hash table template.

runtime/vm/object.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_H_
 #define VM_OBJECT_H_
 
 #include <limits>
 #include "include/dart_api.h"
 #include "platform/assert.h"
@@ skipping 5590 matching lines @@
                            CallbackType new_symbol,
                            Snapshot::Kind kind);
 
   intptr_t EscapedString(char* buffer, int max_len) const;
   intptr_t EscapedStringLen(intptr_t tooLong) const;
 
   FINAL_HEAP_OBJECT_IMPLEMENTATION(String, Instance);
 
   friend class Class;
   friend class Symbols;
+  friend class StringSlice;  // SetHash
+  template<typename CharType> friend class CharArray;  // SetHash
   friend class OneByteString;
   friend class TwoByteString;
   friend class ExternalOneByteString;
   friend class ExternalTwoByteString;
   // So that the MarkingVisitor can print a debug string from a NoHandleScope.
   friend class MarkingVisitor;
 };
 
 
 class OneByteString : public AllStatic {
@@ skipping 1596 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_