Add List.insert.

runtime/lib/growable_array.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.
 
 class _GrowableObjectArray<T> implements List<T> {
   factory _GrowableObjectArray._uninstantiable() {
     throw new UnsupportedError(
         "GrowableObjectArray can only be allocated by the VM");
   }
 
+  void insert(int index, T element) {
+    if (index < 0 || index > length) {
+      throw new RangeError.range(index, 0, length);
+    }
+    if (index == this.length) {
+      add(element);
+      return;
+    }
+    int oldLength = this.length;
+    // We are modifying the length just below the is-check. Without the check
+    // Array.copy could throw an exception, leaving the list in a bad state
+    // (with a length that has been increased, but without a new element).
+    if (index is! int) throw new ArgumentError(index);
+    this.length++;
+    Arrays.copy(this,
+                index,
+                this,
+                index + 1,
+                oldLength - index);
+    this[index] = element;
+  }
+
   T removeAt(int index) {
     if (index is! int) throw new ArgumentError(index);
     T result = this[index];
     int newLength = this.length - 1;
     Arrays.copy(this,
                 index + 1,
                 this,
                 index,
                 newLength - index);
     this.length = newLength;
@@ skipping 300 matching lines @@
   }
 
   Set<T> toSet() {
     return new Set<T>.from(this);
   }
 
   Map<int, T> asMap() {
     return IterableMixinWorkaround.asMapList(this);
   }
 }