Remove generic typedefs that dart2js chokes on.

dart/sdk/lib/core/iterable.dart

 // Copyright (c) 2011, 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.core;
 
 /**
  * The [Iterable] interface allows to get an [Iterator] out of an
  * [Iterable] object.
  *
@@ skipping 354 matching lines @@
       remaining--;
     }
     throw new RangeError.value(index);
   }
 }
 
 typedef T _Transformation<S, T>(S value);
 
 class MappedIterable<S, T> extends Iterable<T> {
   final Iterable<S> _iterable;
-  final _Transformation<S, T> _f;
+  // TODO(ahe): Restore type when feature is implemented in dart2js
+  // checked mode.
+  final /* _Transformation<S, T> */ _f;
 
   MappedIterable(this._iterable, T this._f(S element));
 
   Iterator<T> get iterator => new MappedIterator<S, T>(_iterable.iterator, _f);
 
   // Length related functions are independent of the mapping.
   int get length => _iterable.length;
   bool get isEmpty => _iterable.isEmpty;
 }
 
 class MappedIterator<S, T> extends Iterator<T> {
   T _current;
   final Iterator<S> _iterator;
-  final _Transformation<S, T> _f;
+  // TODO(ahe): Restore type when feature is implemented in dart2js
+  // checked mode.
+  final /* _Transformation<S, T> */ _f;
 
   MappedIterator(this._iterator, T this._f(S element));
 
   bool moveNext() {
     if (_iterator.moveNext()) {
       _current = _f(_iterator.current);
       return true;
     } else {
       _current = null;
       return false;
@@ skipping 165 matching lines @@
       _hasSkipped = true;
       while (_iterator.moveNext()) {
         if (!_f(_iterator.current)) return true;
       }
     }
     return _iterator.moveNext();
   }
 
   E get current => _iterator.current;
 }