Add Timer implementation for dart2js. Also moves tests to appropriate location.

lib/isolate/dart2js/isolateimpl.dart

 // Copyright (c) 2012, 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.
 
 /**
  * Concepts used here:
  *
  * "manager" - A manager contains one or more isolates, schedules their
  * execution, and performs other plumbing on their behalf.  The isolate
  * present at the creation of the manager is designated as its "root isolate".
@@ skipping 199 matching lines @@
 
   /** Unregister a port on this isolate. */
   void unregister(int portId) {
     ports.remove(portId);
     if (ports.isEmpty()) {
       _globalState.isolates.remove(id); // indicate this isolate is not active
     }
   }
 }
 
-// We don't want to import the DOM library just because of window.setTimeout,
-// so we reconstruct the Window class here. The only conflict that could happen
-// with the other DOMWindow class would be because of subclasses.
-// Currently, none of the two Dart classes have subclasses.
-typedef void _TimeoutHandler();
-class _Window native "@*DOMWindow" {
-  int setTimeout(_TimeoutHandler handler, int timeout) native;
-}
-_Window get _window() native
-    """return typeof window != 'undefined' ? window : (void 0);""";
-
 /** Represent the event loop on a javascript thread (DOM or worker). */
 class _EventLoop {
   Queue<_IsolateEvent> events;
 
   _EventLoop() : events = new Queue<_IsolateEvent>();
 
   void enqueue(isolate, fn, msg) {
     events.addLast(new _IsolateEvent(isolate, fn, msg));
   }
 
@@ skipping 26 matching lines @@
     }
     event.process();
     return true;
   }
 
   /**
    * Runs multiple iterations of the run-loop. If possible, each iteration is
    * run asynchronously.
    */
   void _runHelper() {
+    // [_window] is defined in timer_provider.dart.
     if (_window != null) {
       // Run each iteration from the browser's top event loop.
       void next() {
         if (!runIteration()) return;
         _window.setTimeout(next, 0);
       }
       next();
     } else {
       // Run synchronously until no more iterations are available.
       while (runIteration()) {}
@@ skipping 259 matching lines @@
       'command': 'start',
       'id': workerId,
       // Note: we serialize replyPort twice because the child worker needs to
       // first deserialize the worker id, before it can correctly deserialize
       // the port (port deserialization is sensitive to what is the current
       // workerId).
       'replyTo': _serializeMessage(replyPort),
       'functionName': functionName }));
   }
 }