Improve string library performance. String concat and indexOf.

runtime/lib/string_buffer_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 StringBuffer {
   static const int _BUFFER_SIZE = 64;
   static const int _PARTS_TO_COMPACT = 128;
   static const int _PARTS_TO_COMPACT_SIZE_LIMIT = _PARTS_TO_COMPACT * 8;
 
   /**
@@ skipping 84 matching lines @@
   /* patch */ void clear() {
     _parts = null;
     _partsCodeUnits = _bufferPosition = _bufferCodeUnitMagnitude = 0;
   }
 
   /** Returns the contents of buffer as a string. */
   /* patch */ String toString() {
     _consumeBuffer();
     return (_partsCodeUnits == 0) ?
         "" :
-        _StringBase._concatAllNative(_parts, 0, _parts.length);
+        _StringBase._concatRange(_parts, 0, _parts.length);
   }
 
   /** Ensures that the buffer has enough capacity to add n code units. */
   void _ensureCapacity(int n) {
     if (_buffer == null) {
       _buffer = new Uint16List(_BUFFER_SIZE);
     } else if (_bufferPosition + n > _buffer.length) {
       _consumeBuffer();
     }
   }
@@ skipping 30 matching lines @@
       }
     }
   }
 
   /**
    * Compacts the last N parts if their average size allows us to save a
    * lot of memory by turning them all into a single part.
    */
   void _compact() {
     if (_partsCodeUnitsSinceCompaction < _PARTS_TO_COMPACT_SIZE_LIMIT) {
-      String compacted = _StringBase._concatAllNative(
+      String compacted = _StringBase._concatRange(
           _parts,
           _partsCompactionIndex,                     // Start
           _partsCompactionIndex + _PARTS_TO_COMPACT  // End
       );
       _parts.length = _parts.length - _PARTS_TO_COMPACT;
       _parts.add(compacted);
     }
     _partsCodeUnitsSinceCompaction = 0;
     _partsCompactionIndex = _parts.length;
   }
 
   /**
    * Create a [String] from the UFT-16 code units in buffer.
    */
   static String _create(Uint16List buffer, int length, bool isLatin1)
       native "StringBuffer_createStringFromUint16Array";
 }