Fix all strong-mode errors and warnings.

lib/src/runner/browser/dartium.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:async';
 import 'dart:convert';
 import 'dart:io';
 
 import 'package:async/async.dart';
 import 'package:path/path.dart' as p;
@@ skipping 10 matching lines @@
 /// so this exposes a bare-bones API. The browser starts as soon as the class is
 /// constructed, and is killed when [close] is called.
 ///
 /// Any errors starting or running the process are reported through [onExit].
 class Dartium extends Browser {
   final name = "Dartium";
 
   final Future<Uri> observatoryUrl;
 
   factory Dartium(url, {String executable, bool debug: false}) {
-    var completer = new Completer.sync();
+    var completer = new Completer<Uri>.sync();
     return new Dartium._(() async {
       if (executable == null) executable = _defaultExecutable();
 
       var dir = createTempDir();
       var process = await Process.start(executable, [
         "--user-data-dir=$dir",
         url.toString(),
         "--disable-extensions",
         "--disable-popup-blocking",
         "--bwsi",
@@ skipping 64 matching lines @@
   /// Returns the Observatory URL for the Dartium executable with the given
   /// [stdout] stream, or `null` if the correct one couldn't be found.
   ///
   /// Dartium prints out three different Observatory URLs when it starts. Only
   /// one of them is connected to the VM instance running the host page, and the
   /// ordering isn't guaranteed, so we need to figure out which one is correct.
   /// We do so by connecting to the VM service via WebSockets and looking for
   /// the Observatory instance that actually contains an isolate, and returning
   /// the corresponding URI.
   static Future<Uri> _getObservatoryUrl(Stream<List<int>> stdout) async {
-    var urlQueue = new StreamQueue(lineSplitter.bind(stdout).map((line) {
+    var urlQueue = new StreamQueue<Uri>(lineSplitter.bind(stdout).map((line) {
       var match = _observatoryRegExp.firstMatch(line);
       return match == null ? null : Uri.parse(match[1]);
     }).where((line) => line != null));
 
     var operations = [
       urlQueue.next,
       urlQueue.next,
       urlQueue.next
-    ].map(_checkObservatoryUrl);
+    ].map((future) => _checkObservatoryUrl(future));
 
     urlQueue.cancel();
 
     /// Dartium will print three possible observatory URLs. For each one, we
     /// check whether it's actually connected to an isolate, indicating that
     /// it's the observatory for the main page. Once we find the one that is, we
     /// cancel the other requests and return it.
-    return inCompletionOrder(operations)
-        .firstWhere((url) => url != null, defaultValue: () => null);
+    return (await inCompletionOrder(operations)
+        .firstWhere((url) => url != null, defaultValue: () => null)) as Uri;
   }
 
   /// If the URL returned by [future] corresponds to the correct Observatory
   /// instance, returns it. Otherwise, returns `null`.
   ///
   /// If the returned operation is canceled before it fires, the WebSocket
   /// connection with the given Observatory will be closed immediately.
   static CancelableOperation<Uri> _checkObservatoryUrl(Future<Uri> future) {
     var webSocket;
     var canceled = false;
-    var completer = new CancelableCompleter(onCancel: () {
+    var completer = new CancelableCompleter<Uri>(onCancel: () {
       canceled = true;
       if (webSocket != null) webSocket.close();
     });
 
     // We've encountered a format we don't understand. Close the web socket and
     // complete to null.
     giveUp() {
       webSocket.close();
       if (!completer.isCompleted) completer.complete();
     }
@@ skipping 85 matching lines @@
         // incorrect WebSocket that already closed.
         return null;
       }
     }).catchError((error, stackTrace) {
       if (!completer.isCompleted) completer.completeError(error, stackTrace);
     });
 
     return completer.operation;
   }
 }