Revert "Add String.replaceFirstMapped."

sdk/lib/_internal/compiler/js_lib/string_helper.dart

Index: sdk/lib/_internal/compiler/js_lib/string_helper.dart
diff --git a/sdk/lib/_internal/compiler/js_lib/string_helper.dart b/sdk/lib/_internal/compiler/js_lib/string_helper.dart
index 77b8ab9c34a95b95cb4c4c44604578362ffed8ee..ff2505729a1b3cce8352be876681941925776479 100644
--- a/sdk/lib/_internal/compiler/js_lib/string_helper.dart
+++ b/sdk/lib/_internal/compiler/js_lib/string_helper.dart
@@ -193,34 +193,21 @@ stringReplaceAllStringFuncUnchecked(receiver, pattern, onMatch, onNonMatch) {
 }
 
 
-stringReplaceFirstUnchecked(receiver, from, to, int startIndex) {
+stringReplaceFirstUnchecked(receiver, from, to, [int startIndex = 0]) {
   if (from is String) {
-    int index = receiver.indexOf(from, startIndex);
+    var index = receiver.indexOf(from, startIndex);
     if (index < 0) return receiver;
     return '${receiver.substring(0, index)}$to'
            '${receiver.substring(index + from.length)}';
-  }
-  if (from is JSSyntaxRegExp) {
+  } else if (from is JSSyntaxRegExp) {
     return startIndex == 0 ?
         stringReplaceJS(receiver, regExpGetNative(from), to) :
         stringReplaceFirstRE(receiver, from, to, startIndex);
+  } else {
+    checkNull(from);
+    // TODO(floitsch): implement generic String.replace (with patterns).
+    throw "String.replace(Pattern) UNIMPLEMENTED";
   }
-  checkNull(from);
-  Iterator<Match> matches = from.allMatches(receiver, startIndex).iterator;
-  if (!matches.moveNext()) return receiver;
-  Match match = matches.current;
-  return '${receiver.substring(0, match.start)}$to'
-         '${receiver.substring(match.end)}';
-}
-
-stringReplaceFirstMappedUnchecked(receiver, from, replace,
-                                  int startIndex) {
-  Iterator<Match> matches = from.allMatches(receiver, startIndex).iterator;
-  if (!matches.moveNext()) return receiver;
-  Match match = matches.current;
-  String replacement = "${replace(match)}";
-  return '${receiver.substring(0, match.start)}$replacement'
-         '${receiver.substring(match.end)}';
 }
 
 stringJoinUnchecked(array, separator) {