make dart2js_info strong-mode clean

lib/src/measurements.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.
 
 /// Measurements collected about individual functions.  Currently we compute
 /// data about "sends", to classify whether we know the target or not.
 library dart2js_info.src.measurements;
 
 /// Top-level set of metrics
 const List<Metric> _topLevelMetrics = const [Metric.functions, Metric.send];
@@ skipping 117 matching lines @@
 
   /// Metyric for calls to more than one possible interceptor, see [send] for
   /// details.
   static const Metric multiInterceptorSend = const Metric('interceptor multi');
 
   /// Metyric for dynamic calls for which we know nothing about the target
   /// method. See [send] for details.
   static const Metric dynamicSend = const Metric('dynamic');
 
   static Map<String, Metric> _nameToMetricMap = () {
-    var res = {};
+    var res = <String, Metric>{};
     visitAllMetrics((m, _) => res[m.name] = m);
     return res;
   }();
 }
 
 /// A metric that is subdivided in smaller metrics.
 class GroupedMetric extends Metric {
   final List<Metric> submetrics;
 
   const GroupedMetric(String name, this.submetrics) : super(name);
@@ skipping 63 matching lines @@
   bool checkInvariant(GroupedMetric key) {
     int total = counters[key] ?? 0;
     int submetricTotal = 0;
     for (var metric in key.submetrics) {
       var n = counters[metric];
       if (n != null) submetricTotal += n;
     }
     return total == submetricTotal;
   }
 }