Revert "Convert _propagateToListeners to using an external stack instead of recursion."

sdk/lib/async/zone.dart

 // Copyright (c) 2013, 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.
 
 part of dart.async;
 
 typedef dynamic ZoneCallback();
 typedef dynamic ZoneUnaryCallback(arg);
 typedef dynamic ZoneBinaryCallback(arg1, arg2);
 
@@ skipping 430 matching lines @@
    */
   void print(String line);
 
   /**
    * Call to enter the Zone.
    *
    * The previous current zone is returned.
    */
   static Zone _enter(Zone zone) {
     assert(zone != null);
+    assert(!identical(zone, _current));
     Zone previous = _current;
     _current = zone;
     return previous;
   }
 
   /**
    * Call to leave the Zone.
    *
    * The previous Zone must be provided as `previous`.
    */
@@ skipping 609 matching lines @@
    *
    * Returns `this` if `this` has an error-handler. Otherwise returns the
    * parent's error-zone.
    */
   Zone get errorZone => this;
 
   // Zone interface.
 
   dynamic runGuarded(f()) {
     try {
-      Zone current = Zone._current;
-      if (identical(current, _ROOT_ZONE) ||
-          identical(current, this)) {
+      if (identical(_ROOT_ZONE, Zone._current)) {
         return f();
       }
-
-      Zone old = Zone._enter(this);
-      try {
-        return f();
-      } finally {
-        Zone._leave(old);
-      }
+      return _rootRun(null, null, this, f);
     } catch (e, s) {
       return handleUncaughtError(e, s);
     }
   }
 
   dynamic runUnaryGuarded(f(arg), arg) {
     try {
       if (identical(_ROOT_ZONE, Zone._current)) {
         return f(arg);
       }
@@ skipping 45 matching lines @@
 
   dynamic handleUncaughtError(error, StackTrace stackTrace) {
     return _rootHandleUncaughtError(null, null, this, error, stackTrace);
   }
 
   Zone fork({ZoneSpecification specification, Map zoneValues}) {
     return _rootFork(null, null, this, specification, zoneValues);
   }
 
   dynamic run(f()) {
-    Zone current = Zone._current;
-    if (identical(current, _ROOT_ZONE) ||
-        identical(current, this)) {
-      return f();
-    }
-
-    Zone old = Zone._enter(this);
-    try {
-      return f();
-    } finally {
-      Zone._leave(old);
-    }
+    if (identical(Zone._current, _ROOT_ZONE)) return f();
+    return _rootRun(null, null, this, f);
   }
 
   dynamic runUnary(f(arg), arg) {
     if (identical(Zone._current, _ROOT_ZONE)) return f(arg);
     return _rootRunUnary(null, null, this, f, arg);
   }
 
   dynamic runBinary(f(arg1, arg2), arg1, arg2) {
     if (identical(Zone._current, _ROOT_ZONE)) return f(arg1, arg2);
     return _rootRunBinary(null, null, this, f, arg1, arg2);
@@ skipping 82 matching lines @@
                                    handleUncaughtError: errorHandler);
   }
   Zone zone = Zone.current.fork(specification: zoneSpecification,
                                 zoneValues: zoneValues);
   if (onError != null) {
     return zone.runGuarded(body);
   } else {
     return zone.run(body);
   }
 }