More optimization of _uriEncode.

sdk/lib/convert/ascii.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.
 
 part of dart.convert;
 
 /**
  * An instance of the default implementation of the [AsciiCodec].
  *
  * This instance provides a convenient access to the most common ASCII
@@ skipping 272 matching lines @@
   Sink _sink;
   _SimpleAsciiDecoderSink(this._sink);
 
   void close() {
     _sink.close();
   }
 
   void add(List<int> source) {
     for (int i = 0; i < source.length; i++) {
       if ((source[i] & ~_ASCII_MASK) != 0) {
-        throw new FormatException("Source contains non-ASCII bytes.");
+        throw new FormatException("Source contains non-ASCII bytes.",
+                                  source, i);
       }
     }
     _sink.add(new String.fromCharCodes(source));
   }
 
   void addSlice(List<int> source, int start, int end, bool isLast) {
     final int length = source.length;
     RangeError.checkValidRange(start, end, length);
     if (start < end) {
       if (start != 0 || end != length) {
         source = source.sublist(start, end);
       }
       add(source);
     }
     if (isLast) close();
   }
 }