VM-internalize the default Map implementation.

runtime/lib/collection_patch.dart

 // Copyright (c) 2013, 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.
 
 patch class HashMap<K, V> {
   /* patch */ factory HashMap({ bool equals(K key1, K key2),
                                 int hashCode(K key),
                                 bool isValidKey(potentialKey) }) {
     if (isValidKey == null) {
       if (hashCode == null) {
@@ skipping 898 matching lines @@
   /// only the head entry itself).
   var _nextEntry;
   var _previousEntry;
 
   /* patch */ factory LinkedHashMap({ bool equals(K key1, K key2),
                                       int hashCode(K key),
                                       bool isValidKey(potentialKey) }) {
     if (isValidKey == null) {
       if (hashCode == null) {
         if (equals == null) {
-          if (_useInternalCached) {
-            return new _InternalLinkedHashMap<K, V>();
-          } else {
-            return new _CompactLinkedHashMap<K, V>();
-          }
+          return new _InternalLinkedHashMap<K, V>();
         }
         hashCode = _defaultHashCode;
       } else {
         if (identical(identityHashCode, hashCode) &&
             identical(identical, equals)) {
           return new _CompactLinkedIdentityHashMap<K, V>();
         }
         if (equals == null) {
           equals = _defaultEquals;
         }
       }
     } else {
       if (hashCode == null) {
         hashCode = _defaultHashCode;
       }
       if (equals == null) {
         equals = _defaultEquals;
       }
     }
     return new _CompactLinkedCustomHashMap<K, V>(equals, hashCode, isValidKey);
   }
 
   /* patch */ factory LinkedHashMap.identity() =
       _CompactLinkedIdentityHashMap<K, V>;
-
-  static final bool _useInternalCached = _useInternal;
-  static bool get _useInternal native "LinkedHashMap_useInternal";
 }
 
 patch class LinkedHashSet<E> {
   /* patch */ factory LinkedHashSet({ bool equals(E e1, E e2),
                                       int hashCode(E e),
                                       bool isValidKey(potentialKey) }) {
     if (isValidKey == null) {
       if (hashCode == null) {
         if (equals == null) {
           return new _CompactLinkedHashSet<E>();
@@ skipping 15 matching lines @@
       if (equals == null) {
         equals = _defaultEquals;
       }
     }
     return new _CompactLinkedCustomHashSet<E>(equals, hashCode, isValidKey);
   }
 
   /* patch */ factory LinkedHashSet.identity() =
       _CompactLinkedIdentityHashSet<E>;
 }