Inline _OneByteString._setAt. The key knowledge is that _setAt is an internal method that has to be…

runtime/lib/string_patch.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.
 
 patch class String {
   /* patch */ factory String.fromCharCodes(Iterable<int> charCodes) {
     return _StringBase.createFromCharCodes(charCodes);
   }
 }
 
@@ skipping 472 matching lines @@
     if ((pattern is _OneByteString) && (pattern.length == 1)) {
       return _splitWithCharCode(pattern.codeUnitAt(0));
     }
     return super.split(pattern);
   }
 
   // Allocates a string of given length, expecting its content to be
   // set using _setAt.
   static _OneByteString _allocate(int length) native "OneByteString_allocate";
 
-  // Code point value must be a valid Latin1 (0..0xFF). Index must be valid.
+  // This is internal helper method. Code point value must be a valid
+  // Latin1 value (0..0xFF), index must be valid.
   void _setAt(int index, int codePoint) native "OneByteString_setAt";
 }
 
 
 class _TwoByteString extends _StringBase implements String {
   factory _TwoByteString._uninstantiable() {
     throw new UnsupportedError(
         "_TwoByteString can only be allocated by the VM");
   }
 
@@ skipping 111 matching lines @@
 class _CodeUnits extends Object with ListMixin<int>,
                                      UnmodifiableListMixin<int> {
   /** The string that this is the code units of. */
   String _string;
 
   _CodeUnits(this._string);
 
   int get length => _string.length;
   int operator[](int i) => _string.codeUnitAt(i);
 }