Fix all strong-mode errors and warnings.

lib/src/runner/configuration.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.
 
 import 'dart:io';
 
 import 'package:boolean_selector/boolean_selector.dart';
 import 'package:collection/collection.dart';
 import 'package:glob/glob.dart';
 import 'package:path/path.dart' as p;
@@ skipping 262 matching lines @@
       int shardIndex,
       int totalShards,
       Timeout timeout,
       Iterable<Pattern> patterns,
       Iterable<TestPlatform> platforms,
       Iterable<String> paths,
       Glob filename,
       Iterable<String> chosenPresets,
       BooleanSelector includeTags,
       BooleanSelector excludeTags,
-      Iterable addTags,
+      Iterable<String> addTags,
       Map<BooleanSelector, Configuration> tags,
       Map<PlatformSelector, Configuration> onPlatform,
       Map<String, Configuration> presets}) {
     _unresolved() => new Configuration._(
         help: help,
         version: version,
         verboseTrace: verboseTrace,
         jsTrace: jsTrace,
         skip: skip,
         skipReason: skipReason,
@@ skipping 73 matching lines @@
           this.shardIndex,
           this.totalShards,
           Timeout timeout,
           Iterable<Pattern> patterns,
           Iterable<TestPlatform> platforms,
           Iterable<String> paths,
           Glob filename,
           Iterable<String> chosenPresets,
           BooleanSelector includeTags,
           BooleanSelector excludeTags,
-          Iterable addTags,
+          Iterable<String> addTags,
           Map<BooleanSelector, Configuration> tags,
           Map<PlatformSelector, Configuration> onPlatform,
           Map<String, Configuration> presets})
       : _help = help,
         _version = version,
         _verboseTrace = verboseTrace,
         _jsTrace = jsTrace,
         _skip = skip,
         testOn = testOn ?? PlatformSelector.all,
         _pauseAfterLoad = pauseAfterLoad,
@@ skipping 31 matching lines @@
     } else if (shardIndex != null) {
       RangeError.checkValueInInterval(
           shardIndex, 0, totalShards - 1, "shardIndex");
     }
   }
 
   /// Returns a [input] as an unmodifiable list or `null`.
   ///
   /// If [input] is `null` or empty, this returns `null`. Otherwise, it returns
   /// `input.toList()`.
-  static List _list(Iterable input) {
+  static List/*<T>*/ _list/*<T>*/(Iterable/*<T>*/ input) {
     if (input == null) return null;
-    input = new List.unmodifiable(input);
-    if (input.isEmpty) return null;
-    return input;
+    var list = new List/*<T>*/.unmodifiable(input);
+    if (list.isEmpty) return null;
+    return list;
   }
 
-  /// Returns an modifiable copy of [input] or an empty unmodifiable map.
-  static Map _map(Map input) {
-    if (input == null) return const {};
+  /// Returns an unmodifiable copy of [input] or an empty unmodifiable map.
+  static Map/*<K, V>*/ _map/*<K, V>*/(Map/*<K, V>*/ input) {
+    if (input == null || input.isEmpty) return const {};
     return new Map.unmodifiable(input);
   }
 
   /// Merges this with [other].
   ///
   /// For most fields, if both configurations have values set, [other]'s value
   /// takes precedence. However, certain fields are merged together instead.
   /// This is indicated in those fields' documentation.
   Configuration merge(Configuration other) {
     if (this == Configuration.empty) return other;
@@ skipping 55 matching lines @@
       int shardIndex,
       int totalShards,
       Timeout timeout,
       Iterable<Pattern> patterns,
       Iterable<TestPlatform> platforms,
       Iterable<String> paths,
       Glob filename,
       Iterable<String> chosenPresets,
       BooleanSelector includeTags,
       BooleanSelector excludeTags,
-      Iterable addTags,
+      Iterable<String> addTags,
       Map<BooleanSelector, Configuration> tags,
       Map<PlatformSelector, Configuration> onPlatform,
       Map<String, Configuration> presets}) {
     return new Configuration(
         help: help ?? _help,
         version: version ?? _version,
         verboseTrace: verboseTrace ?? _verboseTrace,
         jsTrace: jsTrace ?? _jsTrace,
         skip: skip ?? _skip,
         skipReason: skipReason ?? this.skipReason,
@@ skipping 22 matching lines @@
 
   /// Merges two maps whose values are [Configuration]s.
   ///
   /// Any overlapping keys in the maps have their configurations merged in the
   /// returned map.
   Map<Object, Configuration> _mergeConfigMaps(Map<Object, Configuration> map1,
           Map<Object, Configuration> map2) =>
       mergeMaps(map1, map2,
           value: (config1, config2) => config1.merge(config2));
 }