Add Resolution and Parsing interfaces for computeType, ensureResolved and parseNode.

tests/compiler/dart2js/parser_helper.dart

 // 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.
 
 library parser_helper;
 
 import "package:expect/expect.dart";
 
 import "package:compiler/src/elements/elements.dart";
 import "package:compiler/src/tree/tree.dart";
@@ skipping 100 matching lines @@
   return node;
 }
 
 Node parseStatement(String text) =>
   parseBodyCode(text, (parser, tokens) => parser.parseStatement(tokens));
 
 Node parseFunction(String text, Compiler compiler) {
   ElementX element = parseUnit(text, compiler, compiler.mainApp).head;
   Expect.isNotNull(element);
   Expect.equals(ElementKind.FUNCTION, element.kind);
-  return element.parseNode(compiler);
+  return element.parseNode(compiler.parsing);
 }
 
 Node parseMember(String text, {DiagnosticListener diagnosticHandler}) {
   return parseBodyCode(text, (parser, tokens) => parser.parseMember(tokens),
                        diagnosticHandler: diagnosticHandler);
 }
 
 class MockFile extends StringSourceFile {
   MockFile(text)
       : super.fromName('<string>', text);
@@ skipping 15 matching lines @@
   ElementListener listener = new ElementListener(compiler, unit, () => id++);
   PartialParser parser = new PartialParser(listener);
   compiler.withCurrentElement(unit, () => parser.parseUnit(tokens));
   return unit.localMembers;
 }
 
 NodeList fullParseUnit(String source, {DiagnosticListener diagnosticHandler}) {
   return parseBodyCode(source, (parser, tokens) => parser.parseUnit(tokens),
                        diagnosticHandler: diagnosticHandler);
 }