Fix all strong mode warnings.

lib/src/trace.dart

 // Copyright (c) 2013, 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:collection';
 import 'dart:math' as math;
 
 import 'chain.dart';
 import 'frame.dart';
 import 'lazy_trace.dart';
@@ skipping 243 matching lines @@
         // internal frames. They only ever show up in stack chains and are
         // always surrounded by other traces that are actually useful, so we can
         // just get rid of them.
         // TODO(nweiz): Get rid of this logic some time after issue 22009 is
         // fixed.
         if (!frame.member.contains('<async>')) return false;
         return frame.line == null;
       };
     }
 
-    var newFrames = [];
+    var newFrames = <Frame>[];
     for (var frame in frames.reversed) {
       if (frame is UnparsedFrame || !predicate(frame)) {
         newFrames.add(frame);
       } else if (newFrames.isEmpty || !predicate(newFrames.last)) {
         newFrames.add(new Frame(
             frame.uri, frame.line, frame.column, frame.member));
       }
     }
 
     if (terse) {
@@ skipping 14 matching lines @@
     var longest = frames.map((frame) => frame.location.length)
         .fold(0, math.max);
 
     // Print out the stack trace nicely formatted.
     return frames.map((frame) {
       if (frame is UnparsedFrame) return "$frame\n";
       return '${padRight(frame.location, longest)}  ${frame.member}\n';
     }).join();
   }
 }