Redirect pure isolate print to helper isolate.

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 3ef960a2ae570346ef041ed830065ef463a7d37a..8bcab03d4f5f5bc7de7dbed328ab2b22792e5083 100644
--- a/tools/dom/src/native_DOMImplementation.dart
+++ b/tools/dom/src/native_DOMImplementation.dart
@@ -58,7 +58,6 @@ class _Utils {
   }
 
   static window() native "Utils_window";
-  static print(String message) native "Utils_print";
   static forwardingPrint(String message) native "Utils_forwardingPrint";
   static void spawnDomFunction(Function topLevelFunction, int replyTo) native "Utils_spawnDomFunction";
   static int _getNewIsolateId() native "Utils_getNewIsolateId";
@@ -132,12 +131,41 @@ class _DOMStringMap extends NativeFieldWrapperClass1 implements Map<String, Stri
   bool get isEmpty => Maps.isEmpty(this);
 }
 
-get _printClosure => (s) {
-  try {
-    window.console.log(s);
-  } catch (_) {
-    _Utils.print(s);
-  }
+final Future<SendPort> _HELPER_ISOLATE_PORT =
+    spawnDomFunction(_helperIsolateMain);
+
+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];
+      final callback = () { replyTo.send(_TIMER_PING); };
+      _TIMER_REGISTRY[replyTo] = periodic ?
+          new Timer.periodic(duration, callback) :
+          new Timer(duration, callback);
+    } 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');

[vsm, 2013/03/29 14:14:54]

We have the id we're using for interop (_Utils._getNewIsolateId) ... if that
works on background isolates.

Do you know if workers print any ID?  That is what dart2js isolates should be
mapping to. 

[Anton Muhin, 2013/03/29 16:14:33]

Sorry, no, I do not immediately now.  Ideally we should probably print something
like root library url and some unique id.

On 2013/03/29 14:14:54, vsm wrote:

+    }
+  });
+}
+
+final _printClosure = window.console.log;

[vsm, 2013/03/29 14:14:54]

Is there a way at the Dart-level to programmatically tell whether I'm on a DOM
isolate (without a try-catch)?  Could use a pattern like:

final _printClosure = _hasDomAccess ? window.console.log :
_pureIsolatePrintClosure;

instead of wiring up in c++.

[Anton Muhin, 2013/03/29 16:14:33]

Not right now.  We can expose it via Utils, but I am not sure if it's worth it
or not.

On 2013/03/29 14:14:54, vsm wrote:

+final _pureIsolatePrintClosure = (s) {
+  _HELPER_ISOLATE_PORT.then((sendPort) {
+    sendPort.send([_PRINT, s]);
+  });
 };
 
 final _forwardingPrintClosure = _Utils.forwardingPrint;