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

sdk/lib/uri/encode_decode.dart

Index: sdk/lib/uri/encode_decode.dart
diff --git a/sdk/lib/uri/encode_decode.dart b/sdk/lib/uri/encode_decode.dart
index 6338518a4a5a290b2dbfe959912ccbbeb07ffbc4..09473f23ca515101d738ebe15ec731c1a3d39ab0 100644
--- a/sdk/lib/uri/encode_decode.dart
+++ b/sdk/lib/uri/encode_decode.dart
@@ -77,22 +77,13 @@ 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 >= 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');
-        }
-      }
+      if (ch >= 0x10000) i++;
       for (int codepoint in codepointsToUtf8([ch])) {
         result.add(byteToHex(codepoint));
       }