Refactor the dart api a bit:

runtime/vm/parser.h

 // Copyright (c) 2011, 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_PARSER_H_
 #define VM_PARSER_H_
 
 #include "include/dart_api.h"
 
 #include "vm/ast.h"
@@ skipping 170 matching lines @@
   // Support for parsing of scripts.
   void ParseTopLevel();
   void ParseClassDefinition(GrowableArray<const Class*>* classes);
   void ParseInterfaceDefinition(GrowableArray<const Class*>* classes);
   void ParseFunctionTypeAlias(GrowableArray<const Class*>* classes);
   void ParseTopLevelVariable(TopLevel* top_level);
   void ParseTopLevelFunction(TopLevel* top_level);
   void ParseTopLevelAccessor(TopLevel* top_level);
 
   // Support for parsing libraries.
-  Dart_Result CallLibraryTagHandler(Dart_LibraryTag tag,
+  Dart_Handle CallLibraryTagHandler(Dart_LibraryTag tag,
                                     intptr_t token_pos,
                                     const String& url);
   void ParseLibraryDefinition();
   void ParseLibraryName();
   void ParseLibraryImport();
   void ParseLibraryInclude();
 
   bool ResolveTypeFromClass(intptr_t type_pos, const Class& cls, Type* type);
   enum TypeResolution {
     kDoNotResolve,  // Type resolution is postponed.
@@ skipping 238 matching lines @@
   TryBlocks* try_blocks_list_;
 
   char error_msg_[kErrorBuflen];
 
   DISALLOW_COPY_AND_ASSIGN(Parser);
 };
 
 }  // namespace dart
 
 #endif  // VM_PARSER_H_