Fix the remaining strong mode warnings.

lib/src/chain.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:async';
 import 'dart:collection';
 import 'dart:math' as math;
 
 import 'frame.dart';
 import 'stack_zone_specification.dart';
@@ skipping 60 matching lines @@
   static /*=T*/ capture/*<T>*/(/*=T*/ callback(),
       {void onError(error, Chain chain), bool when: true}) {
     if (!when) {
       var newOnError;
       if (onError != null) {
         newOnError = (error, stackTrace) {
           onError(error, new Chain.forTrace(stackTrace));
         };
       }
 
-      return runZoned(callback, onError: newOnError);
+      // TODO(rnystrom): Remove this cast if runZoned() gets a generic type.
+      return runZoned(callback, onError: newOnError) as dynamic/*=T*/;
     }
 
     var spec = new StackZoneSpecification(onError);
     return runZoned(() {
       try {
         return callback();
       } catch (error, stackTrace) {
         // TODO(nweiz): Don't special-case this when issue 19566 is fixed.
         return Zone.current.handleUncaughtError(error, stackTrace);
       }
     }, zoneSpecification: spec.toSpec(), zoneValues: {
       #stack_trace.stack_zone.spec: spec
-    });
+    }) as dynamic/*=T*/;
+    // TODO(rnystrom): Remove this cast if runZoned() gets a generic type.
   }
 
   /// Returns [futureOrStream] unmodified.
   ///
   /// Prior to Dart 1.7, this was necessary to ensure that stack traces for
   /// exceptions reported with [Completer.completeError] and
   /// [StreamController.addError] were tracked correctly.
   @Deprecated("Chain.track is not necessary in Dart 1.7+.")
   static track(futureOrStream) => futureOrStream;
 
@@ skipping 99 matching lines @@
 
     // Don't call out to [Trace.toString] here because that doesn't ensure that
     // padding is consistent across all traces.
     return traces.map((trace) {
       return trace.frames.map((frame) {
         return '${padRight(frame.location, longest)}  ${frame.member}\n';
       }).join();
     }).join(chainGap);
   }
 }