Use zone allocated C-strings instead of String heap objects to construct signature symbols

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 "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 2682 matching lines @@
   void set_eval_script(const Script& value) const;
   void set_num_optional_parameters(intptr_t value) const;  // Encoded value.
   void set_kind_tag(intptr_t value) const;
   void set_data(const Object& value) const;
 
   static RawFunction* New();
 
   void BuildSignatureParameters(bool instantiate,
                                 NameVisibility name_visibility,
                                 const TypeArguments& instantiator,
-                                const GrowableObjectArray& pieces) const;
+                                GrowableArray<const String*>* pieces) const;
   RawString* BuildSignature(bool instantiate,
                             NameVisibility name_visibility,
                             const TypeArguments& instantiator) const;
 
   // Check the subtype or 'more specific' relationship.
   bool TypeTest(TypeTestKind test_kind,
                 const TypeArguments& type_arguments,
                 const Function& other,
                 const TypeArguments& other_type_arguments,
                 Error* bound_error) const;
@@ skipping 5334 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_