Remove spawnDomIsolate code

tools/dom/src/native_DOMImplementation.dart

Index: tools/dom/src/native_DOMImplementation.dart
diff --git a/tools/dom/src/native_DOMImplementation.dart b/tools/dom/src/native_DOMImplementation.dart
index 8991ee140adbac41c3e9300cdc05b3dc95839f99..bba784b2d5026c9092ec504077abcb61ac06883c 100644
--- a/tools/dom/src/native_DOMImplementation.dart
+++ b/tools/dom/src/native_DOMImplementation.dart
@@ -106,7 +106,6 @@ class _Utils {
 
   static window() native "Utils_window";
   static forwardingPrint(String message) native "Utils_forwardingPrint";
-  static void spawnDomFunction(Function f, int replyTo) native "Utils_spawnDomFunction";
   static int _getNewIsolateId() native "Utils_getNewIsolateId";
 
   // The following methods were added for debugger integration to make working
@@ -366,79 +365,10 @@ class _DOMStringMap extends NativeFieldWrapperClass1 implements Map<String, Stri
   bool get isNotEmpty => Maps.isNotEmpty(this);
 }
 
-// TODO(vsm): Remove DOM isolate code.  This is only used to support
-// printing and timers in background isolates.  Background isolates
-// should just forward to the main DOM isolate instead of requiring a
-// special DOM isolate.
-
-_makeSendPortFuture(spawnRequest) {
-  final completer = new Completer<SendPort>.sync();
-  final port = new ReceivePort();
-  port.receive((result, _) {
-    completer.complete(result);
-    port.close();
-  });
-  // TODO: SendPort.hashCode is ugly way to access port id.
-  spawnRequest(port.toSendPort().hashCode);
-  return completer.future;
-}
-
-Future<SendPort> _spawnDomFunction(Function f) =>
-    _makeSendPortFuture((portId) { _Utils.spawnDomFunction(f, portId); });
-
-final Future<SendPort> __HELPER_ISOLATE_PORT =
-    _spawnDomFunction(_helperIsolateMain);
-
-// Tricky part.
-// Once __HELPER_ISOLATE_PORT gets resolved, it will still delay in .then
-// and to delay Timer.run is used. However, Timer.run will try to register
-// another Timer and here we got stuck: event cannot be posted as then
-// callback is not executed because it's delayed with timer.
-// Therefore once future is resolved, it's unsafe to call .then on it
-// in Timer code.
-SendPort __SEND_PORT;
-
-_sendToHelperIsolate(msg, SendPort replyTo) {
-  if (__SEND_PORT != null) {
-    __SEND_PORT.send(msg, replyTo);
-  } else {
-    __HELPER_ISOLATE_PORT.then((port) {
-      __SEND_PORT = port;
-      __SEND_PORT.send(msg, replyTo);
-    });
-  }
-}
-
-final _TIMER_REGISTRY = new Map<SendPort, Timer>();
-
-const _NEW_TIMER = 'NEW_TIMER';
-const _CANCEL_TIMER = 'CANCEL_TIMER';
-const _TIMER_PING = 'TIMER_PING';
-const _PRINT = 'PRINT';
-
-_helperIsolateMain() {
-  port.receive((msg, replyTo) {
-    final cmd = msg[0];
-    if (cmd == _NEW_TIMER) {
-      final duration = new Duration(milliseconds: msg[1]);
-      bool periodic = msg[2];
-      ping() { replyTo.send(_TIMER_PING); };
-      _TIMER_REGISTRY[replyTo] = periodic ?
-          new Timer.periodic(duration, (_) { ping(); }) :
-          new Timer(duration, ping);
-    } else if (cmd == _CANCEL_TIMER) {
-      _TIMER_REGISTRY.remove(replyTo).cancel();
-    } else if (cmd == _PRINT) {
-      final message = msg[1];
-      // TODO(antonm): we need somehow identify those isolates.
-      print('[From isolate] $message');
-    }
-  });
-}
-
 final _printClosure = window.console.log;
 final _pureIsolatePrintClosure = (s) {
-  _sendToHelperIsolate([_PRINT, s], null);
+  throw new UnimplementedError("Printing from a background isolate "
+                               "is not supported in the browser");
 };
 
 final _forwardingPrintClosure = _Utils.forwardingPrint;
@@ -477,43 +407,7 @@ get _timerFactoryClosure =>
   return new _Timer(milliSeconds, callback, repeating);
 };
 
-
-class _PureIsolateTimer implements Timer {
-  bool _isActive = true;
-  final ReceivePort _port = new ReceivePort();
-  SendPort _sendPort; // Effectively final.
-
-  static SendPort _SEND_PORT;
-
-  _PureIsolateTimer(int milliSeconds, callback, repeating) {
-    _sendPort = _port.toSendPort();
-    _port.receive((msg, replyTo) {
-      assert(msg == _TIMER_PING);
-      _isActive = repeating;
-      callback(this);
-      if (!repeating) _cancel();
-    });
-
-    _send([_NEW_TIMER, milliSeconds, repeating]);
-  }
-
-  void cancel() {
-    _cancel();
-    _send([_CANCEL_TIMER]);
-  }
-
-  void _cancel() {
-    _isActive = false;
-    _port.close();
-  }
-
-  _send(msg) {
-    _sendToHelperIsolate(msg, _sendPort);
-  }
-
-  bool get isActive => _isActive;
-}
-
 get _pureIsolateTimerFactoryClosure =>
     ((int milliSeconds, void callback(Timer time), bool repeating) =>
-        new _PureIsolateTimer(milliSeconds, callback, repeating));
+  throw new UnimplementedError("Timers on background isolates "
+                               "are not supported in the browser"));