Fix hot dynamic check in WhereIterator

sdk/lib/internal/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._internal;
 
 /**
  * Marker interface for [Iterable] subclasses that have an efficient
  * [length] implementation.
  */
@@ skipping 411 matching lines @@
   WhereIterable(this._iterable, this._f);
 
   Iterator<E> get iterator => new WhereIterator<E>(_iterable.iterator, _f);
 
   // Specialization of [Iterable.map] to non-EfficientLengthIterable.
   Iterable<T> map<T>(T f(E element)) => new MappedIterable<E, T>._(this, f);
 }
 
 class WhereIterator<E> extends Iterator<E> {
   final Iterator<E> _iterator;
-  final _ElementPredicate _f;
+  final _ElementPredicate<E> _f;
 
   WhereIterator(this._iterator, this._f);
 
   bool moveNext() {
     while (_iterator.moveNext()) {
       if (_f(_iterator.current)) {

[vsm, 2017/04/27 13:29:28]

The change above removes the dynamic check on _f here.

         return true;
       }
     }
     return false;
   }
 
   E get current => _iterator.current;
 }
 
 typedef Iterable<T> _ExpandFunction<S, T>(S sourceElement);
@@ skipping 313 matching lines @@
  * Creates errors throw by [Iterable] when the element count is wrong.
  */
 abstract class IterableElementError {
   /** Error thrown thrown by, e.g., [Iterable.first] when there is no result. */
   static StateError noElement() => new StateError("No element");
   /** Error thrown by, e.g., [Iterable.single] if there are too many results. */
   static StateError tooMany() => new StateError("Too many elements");
   /** Error thrown by, e.g., [List.setRange] if there are too few elements. */
   static StateError tooFew() => new StateError("Too few elements");
 }