Fix all strong-mode errors and warnings.

lib/src/runner/browser/phantom_js.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:io';
 
 import 'package:path/path.dart' as p;
 
 import '../../util/exit_codes.dart' as exit_codes;
@@ skipping 22 matching lines @@
 
 /// A class for running an instance of PhantomJS.
 ///
 /// Any errors starting or running the process are reported through [onExit].
 class PhantomJS extends Browser {
   final name = "PhantomJS";
 
   final Future<Uri> remoteDebuggerUrl;
 
   factory PhantomJS(url, {String executable, bool debug: false}) {
-    var remoteDebuggerCompleter = new Completer.sync();
+    var remoteDebuggerCompleter = new Completer<Uri>.sync();
     return new PhantomJS._(() async {
       if (executable == null) {
         executable = Platform.isWindows ? "phantomjs.exe" : "phantomjs";
       }
 
       var dir = createTempDir();
       var script = p.join(dir, "script.js");
       new File(script).writeAsStringSync(_script);
 
       var port = debug ? await getUnsafeUnusedPort() : null;
 
-      var args = [];
+      var args = <String>[];
       if (debug) {
         args.addAll([
           "--remote-debugger-port=$port",
           "--remote-debugger-autorun=yes"
         ]);
       }
       args.addAll([script, url.toString()]);
       var process = await Process.start(executable, args);
 
       // PhantomJS synchronously emits standard output, which means that if we
@@ skipping 16 matching lines @@
         remoteDebuggerCompleter.complete(null);
       }
 
       return process;
     }, remoteDebuggerCompleter.future);
   }
 
   PhantomJS._(Future<Process> startBrowser(), this.remoteDebuggerUrl)
       : super(startBrowser);
 }