Add String.replaceFirstMapped.

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

Index: sdk/lib/_internal/compiler/js_lib/js_string.dart
diff --git a/sdk/lib/_internal/compiler/js_lib/js_string.dart b/sdk/lib/_internal/compiler/js_lib/js_string.dart
index 67f37d500cedbd5a5f89ac27f7a2a0321f3431fe..e682626f8d7200b197e511320b2d27497687ed22 100644
--- a/sdk/lib/_internal/compiler/js_lib/js_string.dart
+++ b/sdk/lib/_internal/compiler/js_lib/js_string.dart
@@ -73,12 +73,18 @@ class JSString extends Interceptor implements String, JSIndexable {
   String replaceFirst(Pattern from, String to, [int startIndex = 0]) {
     checkString(to);
     checkInt(startIndex);
-    if (startIndex < 0 || startIndex > this.length) {
-      throw new RangeError.range(startIndex, 0, this.length);
-    }
+    RangeError.checkValueInInterval(startIndex, 0, this.length, "startIndex");
     return stringReplaceFirstUnchecked(this, from, to, startIndex);
   }
 
+  String replaceFirstMapped(Pattern from, String replace(Match match),
+                            [int startIndex = 0]) {
+    checkNull(replace);
+    checkInt(startIndex);
+    RangeError.checkValueInInterval(startIndex, 0, this.length, "startIndex");
+    return stringReplaceFirstMappedUnchecked(this, from, replace, startIndex);
+  }
+
   List<String> split(Pattern pattern) {
     checkNull(pattern);
     if (pattern is String) {