Rewrite Zone implementation to avoid recursively looking up stuff in the parent chain.

sdk/lib/_internal/lib/async_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.
 
 // Patch file for the dart:async library.
 
 import 'dart:_js_helper' show
     patch,
     Primitives,
     convertDartClosureToJS,
     loadDeferredLibrary;
 import 'dart:_isolate_helper' show
     IsolateNatives,
     TimerImpl,
     leaveJsAsync,
     enterJsAsync,
     isWorker;
 
 import 'dart:_foreign_helper' show JS;
 
 @patch
-Timer _createTimer(Duration duration, void callback()) {
-  int milliseconds = duration.inMilliseconds;
-  if (milliseconds < 0) milliseconds = 0;
-  return new TimerImpl(milliseconds, callback);
-}
-
-@patch
-Timer _createPeriodicTimer(Duration duration,
-                           void callback(Timer timer)) {
-  int milliseconds = duration.inMilliseconds;
-  if (milliseconds < 0) milliseconds = 0;
-  return new TimerImpl.periodic(milliseconds, callback);
-}
-
-@patch
 class _AsyncRun {
   @patch
   static void _scheduleImmediate(void callback()) {
     scheduleImmediateClosure(callback);
   }
 
   // Lazily initialized.
   static final Function scheduleImmediateClosure =
       _initializeScheduleImmediate();
 
@@ skipping 10 matching lines @@
     internalCallback() {
       leaveJsAsync();
       callback();
     };
     enterJsAsync();
     JS('void', 'self.scheduleImmediate(#)',
        convertDartClosureToJS(internalCallback, 0));
   }
 
   static void _scheduleImmediateWithTimer(void callback()) {
-    _createTimer(Duration.ZERO, callback);
+    Timer._createTimer(Duration.ZERO, callback);
   }
 }
 
 @patch
 class DeferredLibrary {
   @patch
   Future<Null> load() {
     return loadDeferredLibrary(libraryName, uri);
   }
 }
 
+@patch
+class Timer {
+  @patch
+  static Timer _createTimer(Duration duration, void callback()) {
+    int milliseconds = duration.inMilliseconds;
+    if (milliseconds < 0) milliseconds = 0;
+    return new TimerImpl(milliseconds, callback);
+  }
+
+  @patch
+  static Timer _createPeriodicTimer(Duration duration,
+                             void callback(Timer timer)) {
+    int milliseconds = duration.inMilliseconds;
+    if (milliseconds < 0) milliseconds = 0;
+    return new TimerImpl.periodic(milliseconds, callback);
+  }
+}
+
 bool get _hasDocument => JS('String', 'typeof document') == 'object';