Create _RootZone and _RootSpecification.

sdk/lib/async/zone.dart

Index: sdk/lib/async/zone.dart
diff --git a/sdk/lib/async/zone.dart b/sdk/lib/async/zone.dart
index 80184c2e75e67f00ef01e7c42e0f269589dbd582..cec32f697a28c725e7d6eecd3189fb1dbf4aedd0 100644
--- a/sdk/lib/async/zone.dart
+++ b/sdk/lib/async/zone.dart
@@ -521,22 +521,22 @@ class _ZoneDelegate implements ZoneDelegate {
 
 
 /**
- * Default implementation of a [Zone].
+ * Base class for Zone implementations.
  */
-class _CustomizedZone implements Zone {
+abstract class _BaseZone implements Zone {
+  const _BaseZone();
+
   /// The parent zone.
-  final _CustomizedZone parent;
+  _BaseZone get parent;
   /// The zone's handlers.
-  final ZoneSpecification _specification;
-  /// The zone's value map.
-  final Map<Symbol, dynamic> _map;
-
-  const _CustomizedZone(this.parent, this._specification, this._map);
-
-  Zone get _errorZone {
-    if (_specification.handleUncaughtError != null) return this;
-    return parent._errorZone;
-  }
+  ZoneSpecification get _specification;
+  /**
+   * The closest error-handling zone.
+   *
+   * Returns `this` if `this` has an error-handler. Otherwise returns the
+   * parent's error-zone.
+   */
+  Zone get _errorZone;
 
   bool inSameErrorZone(Zone otherZone) => _errorZone == otherZone._errorZone;
 
@@ -591,6 +591,25 @@ class _CustomizedZone implements Zone {
       return (arg1, arg2) => this.runBinary(registered, arg1, arg2);
     }
   }
+}
+
+
+/**
+ * Default implementation of a [Zone].
+ */
+class _CustomizedZone extends _BaseZone {
+  final _BaseZone parent;
+  final ZoneSpecification _specification;
+
+  /// The zone's value map.
+  final Map<Symbol, dynamic> _map;
+
+  const _CustomizedZone(this.parent, this._specification, this._map);
+
+  Zone get _errorZone {
+    if (_specification.handleUncaughtError != null) return this;
+    return parent._errorZone;
+  }
 
   operator [](Symbol key) {
     var result = _map[key];
@@ -756,22 +775,80 @@ Zone _rootFork(Zone self, ZoneDelegate parent, Zone zone,
   return new _CustomizedZone(zone, specification, copiedMap);
 }
 
-const _ROOT_SPECIFICATION = const ZoneSpecification(
-  handleUncaughtError: _rootHandleUncaughtError,
-  run: _rootRun,
-  runUnary: _rootRunUnary,
-  runBinary: _rootRunBinary,
-  registerCallback: _rootRegisterCallback,
-  registerUnaryCallback: _rootRegisterUnaryCallback,
-  registerBinaryCallback: _rootRegisterBinaryCallback,
-  scheduleMicrotask: _rootScheduleMicrotask,
-  createTimer: _rootCreateTimer,
-  createPeriodicTimer: _rootCreatePeriodicTimer,
-  fork: _rootFork
-);
-
-const _ROOT_ZONE =
-    const _CustomizedZone(null, _ROOT_SPECIFICATION, const <Symbol, dynamic>{});
+class _RootZoneSpecification implements ZoneSpecification {
+  const _RootZoneSpecification();
+
+  HandleUncaughtErrorHandler get handleUncaughtError =>
+      _rootHandleUncaughtError;
+  RunHandler get run => _rootRun;
+  RunUnaryHandler get runUnary => _rootRunUnary;
+  RunBinaryHandler get runBinary => _rootRunBinary;
+  RegisterCallbackHandler get registerCallback => _rootRegisterCallback;
+  RegisterUnaryCallbackHandler get registerUnaryCallback =>
+      _rootRegisterUnaryCallback;
+  RegisterBinaryCallbackHandler get registerBinaryCallback =>
+      _rootRegisterBinaryCallback;
+  ScheduleMicrotaskHandler get scheduleMicrotask => _rootScheduleMicrotask;
+  @deprecated
+  RunAsyncHandler get runAsync => null;
+  CreateTimerHandler get createTimer => _rootCreateTimer;
+  CreatePeriodicTimerHandler get createPeriodicTimer =>
+      _rootCreatePeriodicTimer;
+  ForkHandler get fork => _rootFork;
+}
+
+class _RootZone extends _BaseZone {
+  const _RootZone();
+
+  Zone get parent => null;
+  ZoneSpecification get _specification => const _RootZoneSpecification();
+  Zone get _errorZone => this;
+
+  bool inSameErrorZone(Zone otherZone) => otherZone._errorZone == this;
+
+  operator [](Symbol key) => null;
+
+  // Methods that can be customized by the zone specification.
+
+  dynamic handleUncaughtError(error, StackTrace stackTrace) =>
+      _rootHandleUncaughtError(this, null, this, error, stackTrace);
+
+  Zone fork({ZoneSpecification specification, Map zoneValues}) =>
+      _rootFork(this, null, this, specification, zoneValues);
+
+  dynamic run(f()) => _rootRun(this, null, this, f);
+
+  dynamic runUnary(f(arg), arg) => _rootRunUnary(this, null, this, f, arg);
+
+  dynamic runBinary(f(arg1, arg2), arg1, arg2) =>
+      _rootRunBinary(this, null, this, f, arg1, arg2);
+
+  ZoneCallback registerCallback(f()) =>
+      _rootRegisterCallback(this, null, this, f);
+
+  ZoneUnaryCallback registerUnaryCallback(f(arg)) =>
+      _rootRegisterUnaryCallback(this, null, this, f);
+
+  ZoneBinaryCallback registerBinaryCallback(f(arg1, arg2)) =>
+      _rootRegisterBinaryCallback(this, null, this, f);
+
+  void scheduleMicrotask(void f()) {
+    _rootScheduleMicrotask(this, null, this, f);
+  }
+
+  @deprecated
+  void runAsync(void f()) {
+    scheduleMicrotask(f);
+  }
+
+  Timer createTimer(Duration duration, void f()) =>
+      _rootCreateTimer(this, null, this, duration, f);
+
+  Timer createPeriodicTimer(Duration duration, void f(Timer timer)) =>
+      _rootCreatePeriodicTimer(this, null, this, duration, f);
+}
+
+const _ROOT_ZONE = const _RootZone();
 
 
 /**