Ensure that hash for a symbol is not set to 0 when it is made external.

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 315 matching lines @@
     SymbolTable table(isolate, vm_isolate->object_store()->symbol_table());
     symbol ^= table.GetOrNull(str);
     table.Release();
   }
   if (symbol.IsNull()) {
     SymbolTable table(isolate, isolate->object_store()->symbol_table());
     symbol ^= table.InsertNewOrGet(str);
     isolate->object_store()->set_symbol_table(table.Release());
   }
   ASSERT(symbol.IsSymbol());
+  ASSERT(symbol.HasHash());
   return symbol.raw();
 }
 
 
 RawString* Symbols::New(const String& str) {
   if (str.IsSymbol()) {
     return str.raw();
   }
   return New(str, 0, str.Length());
 }
@@ skipping 43 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