Reapply fast-URI patch.

runtime/lib/uri_patch.dart

Index: runtime/lib/uri_patch.dart
diff --git a/runtime/lib/uri_patch.dart b/runtime/lib/uri_patch.dart
index d30953150a6f1ce6aa2c6bd3cb186304d901ad4f..0ce6b11b1685202700cf8338438aae26c774d573 100644
--- a/runtime/lib/uri_patch.dart
+++ b/runtime/lib/uri_patch.dart
@@ -16,18 +16,20 @@ Uri _unsupportedUriBase() {
 _UriBaseClosure _uriBaseClosure = _unsupportedUriBase;
 
 @patch class Uri {
-  static final bool _isWindowsCached = _isWindowsPlatform;
-
-  @patch static bool get _isWindows => _isWindowsCached;
-
   @patch static Uri get base => _uriBaseClosure();
+}
+
+@patch class _Uri {
+  static final bool _isWindowsCached = _isWindowsPlatform;
 
   static bool get _isWindowsPlatform native "Uri_isWindowsPlatform";
 
+  @patch static bool get _isWindows => _isWindowsCached;
+
   @patch static String _uriEncode(List<int> canonicalTable,
-                                        String text,
-                                        Encoding encoding,
-                                        bool spaceToPlus) {
+                                       String text,
+                                       Encoding encoding,
+                                       bool spaceToPlus) {
     // First check if the text will be changed by encoding.
     int i = 0;
     if (identical(encoding, UTF8) ||