Move Iterable implementation to collection.

sdk/lib/_internal/compiler/implementation/lib/collection_patch.dart

Index: sdk/lib/_internal/compiler/implementation/lib/collection_patch.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/collection_patch.dart b/sdk/lib/_internal/compiler/implementation/lib/collection_patch.dart
index 1fd94cd2ad685e6b1a0a6f9604079ae1d93b9dae..10afb9a49fb2fd2871071cdfe5673837ceb36c52 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/collection_patch.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/collection_patch.dart
@@ -301,7 +301,7 @@ patch class HashMap<K, V> {
   }
 }
 
-class HashMapKeyIterable<E> extends Iterable<E> {
+class HashMapKeyIterable<E> extends IterableBase<E> {
   final _map;
   HashMapKeyIterable(this._map);
 
@@ -653,7 +653,7 @@ class LinkedHashMapCell {
   LinkedHashMapCell(this._key, this._value);
 }
 
-class LinkedHashMapKeyIterable<E> extends Iterable<E> {
+class LinkedHashMapKeyIterable<E> extends IterableBase<E> {
   final _map;
   LinkedHashMapKeyIterable(this._map);
 
@@ -1316,4 +1316,4 @@ class LinkedHashSetIterator<E> implements Iterator<E> {
       return true;
     }
   }
-}
+}