Implement scheduleImmediate for the VM.

runtime/lib/isolate_patch.dart

Index: runtime/lib/isolate_patch.dart
diff --git a/runtime/lib/isolate_patch.dart b/runtime/lib/isolate_patch.dart
index 46e4f4039fb0280e74acec775d4b2dd9a71c2e31..d2755f31f5d46088ed8005a107e3c4d31a1f2f90 100644
--- a/runtime/lib/isolate_patch.dart
+++ b/runtime/lib/isolate_patch.dart
@@ -57,6 +57,28 @@ class _ReceivePortImpl extends Stream implements ReceivePort {
   StreamController _controller;
 }
 
+typedef void ImmediateCallback();
+
+/// The callback that has been registered through `scheduleImmediate`.
+ImmediateCallback _pendingImmediateCallback;
+
+/// The closure that should be used as scheduleImmediateClosure, when the VM
+/// is responsible for the event loop.
+void _isolateScheduleImmediate(void callback()) {
+  assert(_pendingImmediateCallback == null);
+  _pendingImmediateCallback = callback;
+}
+
+/// Provide closurized access to _isolateScheduleImmediate.
+/// This makes it easier for embedders to set the scheduleImmediate closure.
+Function get _isolateScheduleImmediateClosure => _isolateScheduleImmediate;

[Ivan Posva, 2013/11/27 22:08:32]

There is one too many ways to get at the closure. Please remove this as it is
more confusing than is worth. All the other embedder defined closures are of the
form _getXYZClosure().

[floitsch, 2013/11/28 19:05:54]

Dartium usually uses getters, but I should be able to adapt their code.
done.

+
+/// The embedder can execute this function to get hold of
+/// [_isolateScheduleImmediate] above.
+Function _getIsolateScheduleImmediateClosure() {
+  return _isolateScheduleImmediate;
+}
+
 class _RawReceivePortImpl implements RawReceivePort {
   factory _RawReceivePortImpl() native "RawReceivePortImpl_factory";
 
@@ -92,7 +114,15 @@ class _RawReceivePortImpl implements RawReceivePort {
   static void _handleMessage(
       _RawReceivePortImpl port, int replyId, var message) {
     assert(port != null);
+    // TODO(floitsch): this relies on the fact that any exception aborts the
+    // VM. Once we have non-fatal global exceptions we need to catch errors
+    // so that we can run the immediate callbacks.
     port._handler(message);
+    if (_pendingImmediateCallback != null) {
+      var callback = _pendingImmediateCallback;
+      _pendingImmediateCallback = null;
+      callback();
+    }
   }
 
   // Call into the VM to close the VM maintained mappings.