Reapply "Fix URI encoding/decoding of + and space""

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 0e94e1f98a2cf18a0124c317f25293c3b4afd743..e8d483bf67174ac291b66fa39cf17100625f3009 100644
--- a/sdk/lib/uri/encode_decode.dart
+++ b/sdk/lib/uri/encode_decode.dart
@@ -22,7 +22,7 @@ part of dart.uri;
  */
 String encodeUri(String uri) {
   return _uriEncode(
-    "-_.!~*'()#;,/?:@&=+\$0123456789"
+    "-_.!~*'()#;,/?:@&=\$0123456789"
     "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz", uri);
 }
 
@@ -82,6 +82,8 @@ String _uriEncode(String canonical, String text) {
   for (int i = 0; i < text.length; i++) {
     if (canonical.indexOf(text[i]) >= 0) {
       result.add(text[i]);
+    } else if (text[i] == " ") {
+      result.add("+");
     } else {
       int ch = text.charCodeAt(i);
       if (ch >= 0xD800 && ch < 0xDC00) {
@@ -137,7 +139,11 @@ String _uriDecode(String text) {
   for (int i = 0; i < text.length;) {
     String ch = text[i];
     if (ch != '%') {
-      result.add(ch);
+      if (ch == '+') {
+        result.add(" ");
+      } else {
+        result.add(ch);
+      }
       i++;
     } else {
       codepoints.clear();