Base JavaScript code position computation on JavaScript tracer.

tests/compiler/dart2js/js_parser_statements_test.dart

 // Copyright (c) 2014, 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.
 
 import 'dart:async';
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
 import 'mock_compiler.dart';
 import 'package:compiler/src/js/js.dart' as jsAst;
 import 'package:compiler/src/js/js.dart' show js;
 
 
 Future testStatement(String statement, arguments, String expect) {
   jsAst.Node node = js.statement(statement, arguments);
   return MockCompiler.create((MockCompiler compiler) {
     String jsText =
-        jsAst.prettyPrint(node, compiler, allowVariableMinification: false)
-        .getText();
+        jsAst.prettyPrint(node, compiler, allowVariableMinification: false);
 
     Expect.stringEquals(expect.trim(), jsText.trim());
   });
 }
 
 Future testError(String statement, arguments, [String expect = ""]) {
   return new Future.sync(() {
     bool doCheck(exception) {
       String message = '$exception';
       Expect.isTrue(message.contains(expect), '"$message" contains "$expect"');
@@ skipping 365 matching lines @@
     testStatement('if (a) {while (true) if (b) {foo1();}} else {foo2();}',
         [], """
 if (a) {
   while (true)
     if (b)
       foo1();
 } else
   foo2();"""),
   ]));
 }