Let Uint16List.setRange detect a String.codeUnits object, and copy directly from the string.

tests/standalone/typed_data_test.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.
 //
 // Dart test program for testing typed data.
 
 // VMOptions=--optimization_counter_threshold=10
 
 // Library tag to be able to run in html test framework.
 library TypedDataTest;
@@ skipping 129 matching lines @@
 
   typed_data.setRange(1, 3, const [8, 9]);
   Expect.equals(20, typed_data[0]);
   Expect.equals(8, typed_data[1]);
   Expect.equals(9, typed_data[2]);
 }
 
 void testSetRange() {
   testSetRangeHelper(new Uint8List(3));
   testSetRangeHelper(new Uint8ClampedList(3));
+  testSetRangeHelper(new Uint16List(3));
+
+  var list = new Uint8List(4);
+  list.setRange(0, 4, "abcd".codeUnits, 0);
+  Expect.listEquals(list, "abcd".codeUnits);
+  list = new Uint16List(4);
+  list.setRange(0, 4, "abcd".codeUnits, 0);
+  Expect.listEquals(list, "abcd".codeUnits);
+  list.setRange(0, 4, "\xff\u0100\uffff\x00".codeUnits, 0);
+  Expect.listEquals(list, "abcd".codeUnits);
 }
 
 class C {
   final x;
   C(this.x);
   operator<(o) => false;
   operator>=(o) => false;
   operator*(o) => x;
 }
 
@@ skipping 262 matching lines @@
   doubleLists.add(new Float32List.fromList(doubleList));
   doubleLists.add(new Float64List.fromList(doubleList));
   for (var ints in intLists) {
     for (var doubles in doubleLists) {
       Expect.throws(() => ints[0] = doubles[0]);
       Expect.throws(() => doubles[0] = ints[0]);
     }
   }
 }
 
+void testStrings() {
+  test(list) {
+    Uint16List uints = new Uint16List(list.length)..setAll(0, list);
+    String string = new String.fromCharCodes(list);
+    for (int i = 0; i < string.length; i++) {
+      for (int j = i; j < string.length; j++) {
+        int length = j - i;
+        {
+          Uint16List copy = new Uint16List(length);
+          copy.setRange(0, length, string.codeUnits, i);
+          Expect.listEquals(uints.sublist(i, j), copy);
+        }
+        {
+          Uint8List buffer = new Uint8List(length * 2 + 8);
+          Uint16List copy = new Uint16List.view(buffer.buffer, 4, length);
+          copy.setRange(0, length, string.codeUnits, i);
+          Expect.listEquals(uints.sublist(i, j), copy);
+        }
+        {
+          String copy = new String.fromCharCodes(uints, i, j);
+          Expect.equals(string.substring(i, j), copy);
+        }
+      }
+    }
+  }
+  test([]);
+  test([0x00, 0x7f, 0xff]);
+  test([0x00, 0xdfff, 0xffff]);
+  test([0xd800, 0xdc00, 0x20, 0xdbff, 0xdfff]);
+}
+
 main() {
   for (int i = 0; i < 20; i++) {
     testCreateUint8TypedData();
     testCreateClampedUint8TypedData();
     testTypedDataRange(false);
     testUnsignedTypedDataRange(false);
     testClampedUnsignedTypedDataRange(false);
     testSetRange();
     testIndexOutOfRange();
     testIndexOf();
@@ skipping 36 matching lines @@
 
     var float64list = new Float64List(16);
     testSetAtIndex(float64list, 1.4260258159703532e-105, true);
     testGetAtIndex(float64list, 1.4260258159703532e-105);
   }
   testTypedDataRange(true);
   testUnsignedTypedDataRange(true);
   testViewCreation();
   testWhere();
   testCreationFromList();
+  testStrings();
 }