Create generic check methods for RangeError causing checks.

sdk/lib/async/stream.dart

Index: sdk/lib/async/stream.dart
diff --git a/sdk/lib/async/stream.dart b/sdk/lib/async/stream.dart
index 5f761aeb9799451e9a27367b8d63e031a78a5b41..3e5d09e1227965c3ba61b535e1f4638932a7f256 100644
--- a/sdk/lib/async/stream.dart
+++ b/sdk/lib/async/stream.dart
@@ -1165,17 +1165,19 @@ abstract class Stream<T> {
     if (index is! int || index < 0) throw new ArgumentError(index);
     _Future<T> future = new _Future<T>();
     StreamSubscription subscription;
+    int elementIndex = 0;
     subscription = this.listen(
       (T value) {
-        if (index == 0) {
+        if (index == elementIndex) {
           _cancelAndValue(subscription, future, value);
           return;
         }
-        index -= 1;
+        elementIndex += 1;
       },
       onError: future._completeError,
       onDone: () {
-        future._completeError(new RangeError.value(index));
+        future._completeError(
+            new RangeError.index(index, this, "index", null, elementIndex));
       },
       cancelOnError: true);
     return future;