Convert all symbols accessor to return read only handles so that it is not necessary to create a ne…

vm/debugger.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/debugger.h"
 
 #include "include/dart_api.h"
 
 #include "vm/code_generator.h"
 #include "vm/code_patcher.h"
@@ skipping 1269 matching lines @@
     imported = lib.ImportLibraryAt(i);
     ASSERT(!imported.IsNull());
     CollectLibraryFields(field_list, imported, prefix_name, false);
   }
   LibraryPrefix& prefix = LibraryPrefix::Handle(isolate_);
   LibraryPrefixIterator it(lib);
   while (it.HasNext()) {
     prefix = it.GetNext();
     prefix_name = prefix.name();
     ASSERT(!prefix_name.IsNull());
-    prefix_name = String::Concat(prefix_name,
-                                 String::Handle(isolate_, Symbols::Dot()));
+    prefix_name = String::Concat(prefix_name, Symbols::Dot());
     for (int i = 0; i < prefix.num_imports(); i++) {
       imported = prefix.GetLibrary(i);
       CollectLibraryFields(field_list, imported, prefix_name, false);
     }
   }
   return Array::MakeArray(field_list);
 }
 
 
 void Debugger::VisitObjectPointers(ObjectPointerVisitor* visitor) {
@@ skipping 339 matching lines @@
 }
 
 
 void Debugger::RegisterCodeBreakpoint(CodeBreakpoint* bpt) {
   ASSERT(bpt->next() == NULL);
   bpt->set_next(code_breakpoints_);
   code_breakpoints_ = bpt;
 }
 
 }  // namespace dart