Make dart:collection strong-mode clean.

sdk/lib/collection/iterable.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.
 
 part of dart.collection;
 
 /**
  * This [Iterable] mixin implements all [Iterable] members except `iterator`.
  *
  * All other methods are implemented in terms of `iterator`.
@@ skipping 103 matching lines @@
 
   Iterable<E> skip(int count) {
     return new SkipIterable<E>(this, count);
   }
 
   Iterable<E> skipWhile(bool test(E value)) {
     return new SkipWhileIterable<E>(this, test);
   }
 
   E get first {
-    Iterator it = iterator;
+    Iterator<E> it = iterator;
     if (!it.moveNext()) {
       throw IterableElementError.noElement();
     }
     return it.current;
   }
 
   E get last {
-    Iterator it = iterator;
+    Iterator<E> it = iterator;
     if (!it.moveNext()) {
       throw IterableElementError.noElement();
     }
     E result;
     do {
       result = it.current;
     } while(it.moveNext());
     return result;
   }
 
   E get single {
-    Iterator it = iterator;
+    Iterator<E> it = iterator;
     if (!it.moveNext()) throw IterableElementError.noElement();
     E result = it.current;
     if (it.moveNext()) throw IterableElementError.tooMany();
     return result;
   }
 
   E firstWhere(bool test(E value), { E orElse() }) {
     for (E element in this) {
       if (test(element)) return element;
     }
@@ skipping 236 matching lines @@
       elision = "...";
       length += ELLIPSIS_SIZE + OVERHEAD;
     }
   }
   if (elision != null) {
     parts.add(elision);
   }
   parts.add(penultimateString);
   parts.add(ultimateString);
 }