Add usage and collision details to the hash table data structure in order to determine effectivenes…

runtime/vm/symbols.cc

 // 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.
 
 #include "vm/symbols.h"
 
 #include "vm/handles.h"
 #include "vm/handles_impl.h"
 #include "vm/hash_table.h"
 #include "vm/isolate.h"
@@ skipping 130 matching lines @@
   String& result = String::Handle(String::Concat(str1_, str2_, Heap::kOld));
   result.SetCanonical();
   result.SetHash(hash_);
   return result.raw();
 }
 
 
 class SymbolTraits {
  public:
   static const char* Name() { return "SymbolTraits"; }
+  static bool ReportStats() { return false; }
 
   static bool IsMatch(const Object& a, const Object& b) {
     const String& a_str = String::Cast(a);
     const String& b_str = String::Cast(b);
     ASSERT(a_str.HasHash());
     ASSERT(b_str.HasHash());
     if (a_str.Hash() != b_str.Hash()) {
       return false;
     }
     intptr_t a_len = a_str.Length();
@@ skipping 594 matching lines @@
 RawObject* Symbols::GetVMSymbol(intptr_t object_id) {
   ASSERT(IsVMSymbolId(object_id));
   intptr_t i = (object_id - kMaxPredefinedObjectIds);
   if ((i > kIllegal) && (i < Symbols::kMaxPredefinedId)) {
     return symbol_handles_[i]->raw();
   }
   return Object::null();
 }
 
 }  // namespace dart