All strong mode cleaning of dart2js.

tests/compiler/dart2js/source_map_validator_helper.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:io';
 import 'dart:convert';
 import 'dart:async';
 
 import 'package:path/path.dart' as path;
 import 'package:expect/expect.dart';
@@ skipping 156 matching lines @@
               if (interval != null &&
                   interval.contains(sourcePosition) &&
                   isInsideElement(localFunction)) {
                 element = localFunction;
               }
             });
           }
           return element;
         }
 
-        void match(AstElement element) {
+        void match(Element _element) {
+          AstElement element = _element;
           Interval interval = intervalFromElement(element);
           if (interval != null && interval.contains(sourcePosition)) {
             AstElement innerElement = findInnermost(element);
             String expectedName = computeElementNameForSourceMaps(innerElement);
             if (name != expectedName) {
               // For the code
               //    (){}();
               //    ^
               // the indicated position is within the scope of the local
               // function but it is also the position for the invocation of it.
@@ skipping 129 matching lines @@
   final Position end;
 
   Interval(this.begin, this.end);
 
   bool contains(Position other) {
     return begin <= other && other <= end;
   }
 
   String toString() => '$begin-$end';
 }