Cleanup URI and use String.replaceRange.

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.
 
 const int _maxAscii = 0x7f;
 const int _maxLatin1 = 0xff;
 const int _maxUtf16 = 0xffff;
 const int _maxUnicode = 0x10ffff;
 
 patch class String {
@@ skipping 561 matching lines @@
                         : pattern.allMatches(this, startIndex).iterator;
     if (!iterator.moveNext()) return this;
     Match match = iterator.current;
     return replaceRange(match.start, match.end, replacement);
   }
 
   String replaceRange(int start, int end, String replacement) {
     int length = this.length;
     end = RangeError.checkValidRange(start, end, length);
     bool replacementIsOneByte = replacement._isOneByte;
+    if (start == 0 && end == length) return replacement;
     int replacementLength = replacement.length;
     int totalLength = start + (length - end) + replacementLength;
     if (replacementIsOneByte && this._isOneByte) {
       var result = _OneByteString._allocate(totalLength);
       int index = 0;
       index = result._setRange(index, this, 0, start);
       index = result._setRange(start, replacement, 0, replacementLength);
       result._setRange(index, this, end, length);
       return result;
     }
@@ skipping 721 matching lines @@
     for (int g in groups) {
       result.add(group(g));
     }
     return result;
   }
 
   final int start;
   final String input;
   final String pattern;
 }