Revert "Add some support for the code-point code-unit distinction."

sdk/lib/uri/encode_decode.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.
 
 /**
  * Javascript-like URI encode/decode functions.
  * The documentation here borrows heavily from the original Javascript
  * doumentation on MDN at:
  * https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects
  */
@@ skipping 59 matching lines @@
 
 /**
  * This is the internal implementation of JavaScript's encodeURI function.
  * It encodes all characters in the string [text] except for those
  * that appear in [canonical], and returns the escaped string.
  */
 String _uriEncode(String canonical, String text) {
   final String hex = '0123456789ABCDEF';
   var byteToHex = (int v) => '%${hex[v >> 4]}${hex[v&0xf]}';
   StringBuffer result = new StringBuffer();
-  // TODO(erikcorry): Use the new character iterator.
   for (int i = 0; i < text.length; i++) {
     if (canonical.indexOf(text[i]) >= 0) {
       result.add(text[i]);
     } else {
       int ch = text.charCodeAt(i);
-      if (ch >= 0x10000) i++;
+      if (ch >= 0xD800 && ch < 0xDC00) {
+        // Low surrogate. We expect a next char high surrogate.
+        ++i;
+        int nextCh = text.length == i ? 0 : text.charCodeAt(i);
+        if (nextCh >= 0xDC00 && nextCh < 0xE000) {
+          // convert the pair to a U+10000 codepoint
+          ch = 0x10000 + ((ch-0xD800) << 10) + (nextCh - 0xDC00);
+        } else {
+          throw new ArgumentError('Malformed URI');
+        }
+      }
       for (int codepoint in codepointsToUtf8([ch])) {
         result.add(byteToHex(codepoint));
       }
     }
   }
   return result.toString();
 }
 
 /**
  * Convert a byte (2 character hex sequence) in string [s] starting
@@ skipping 33 matching lines @@
         if (i == text.length)
           break;
         ch = text[i];
       }
       result.add(decodeUtf8(codepoints));
     }
   }
   return result.toString();
 }