Reduce timer stack overhead by getting immediate callback and run it, instead of calling through fu…

runtime/lib/isolate_patch.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.
 
 import "dart:collection" show HashMap;
 import "dart:_internal";
 
 patch class ReceivePort {
   /* patch */ factory ReceivePort() = _ReceivePortImpl;
 
@@ skipping 79 matching lines @@
 }
 
 void _runPendingImmediateCallback() {
   if (_pendingImmediateCallback != null) {
     var callback = _pendingImmediateCallback;
     _pendingImmediateCallback = null;
     callback();
   }
 }
 
+ImmediateCallback _removePendingImmediateCallback() {
+  var callback = _pendingImmediateCallback;
+  _pendingImmediateCallback = null;
+  return callback;
+}
+
 /// 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";
 
   close() {
@@ skipping 299 matching lines @@
   static Isolate _getCurrentIsolate() {
     List portAndCapabilities = _getPortAndCapabilitiesOfCurrentIsolate();
     return new Isolate(portAndCapabilities[0],
                        pauseCapability: portAndCapabilities[1],
                        terminateCapability: portAndCapabilities[2]);
   }
 
   static List _getPortAndCapabilitiesOfCurrentIsolate()
       native "Isolate_getPortAndCapabilitiesOfCurrentIsolate";
 }