dart2js: run dartfmt on tests

tests/compiler/dart2js/sourcemaps/trace_graph.dart

 // Copyright (c) 2015, 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 sourcemap.trace_graph;
 
 import 'dart:collection';
 
 import 'package:compiler/src/io/source_information.dart';
 import 'package:compiler/src/io/position_information.dart';
@@ skipping 41 matching lines @@
   final node;
   final Offset offset;
   final List text;
   final SourceLocation sourceLocation;
 
   TraceStep next;
   Map<dynamic, TraceStep> branchMap;
 
   List stack;
 
-  TraceStep(
-      this.kind,
-      this.id,
-      this.node,
-      this.offset,
-      this.text,
+  TraceStep(this.kind, this.id, this.node, this.offset, this.text,
       [this.sourceLocation]);
 
   String toString() => '<span style="background:${toColorCss(id)}">$id</span>';
 }
-