Add info about which command line was used to start a browser.

tools/testing/dart/browser_controller.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.
 library browser;
 
 import "dart:async";
 import "dart:convert" show LineSplitter, UTF8, JSON;
 import "dart:core";
 import "dart:io";
 
@@ skipping 130 matching lines @@
 
   /**
    * Start the browser using the supplied argument.
    * This sets up the error handling and usage logging.
    */
   Future<bool> startBrowser(String command,
                             List<String> arguments,
                             {Map<String,String> environment}) {
     return Process.start(command, arguments, environment: environment)
         .then((startedProcess) {
+      _logEvent("Started browser using $command ${arguments.join(' ')}");
       process = startedProcess;
       // Used to notify when exiting, and as a return value on calls to
       // close().
       var doneCompleter = new Completer();
       done = doneCompleter.future;
 
       Completer stdoutDone = new Completer();
       Completer stderrDone = new Completer();
 
       bool stdoutIsDone = false;
@@ skipping 1624 matching lines @@
     </div>
     <div id="embedded_iframe_div" class="test box">
       <iframe style="width:100%;height:100%;" id="embedded_iframe"></iframe>
     </div>
   </body>
 </html>
 """;
     return driverContent;
   }
 }