Update range errors to agree on the numbers.

sdk/lib/core/errors.dart

Index: sdk/lib/core/errors.dart
diff --git a/sdk/lib/core/errors.dart b/sdk/lib/core/errors.dart
index 0e99b0b271ce48375f613c2fc9522aad6d0e5019..ad940cf83843522db98d5e4d258e653d4b5fa74b 100644
--- a/sdk/lib/core/errors.dart
+++ b/sdk/lib/core/errors.dart
@@ -396,6 +396,8 @@ class IndexError extends ArgumentError implements RangeError {
     var explanation = ": index should be less than $length";
     if (invalidValue < 0) {
       explanation = ": index must not be negative";
+    } else if (length == 0) {
+      explanation = ": list is empty";

[floitsch, 2015/09/08 10:54:19]

I don't think we should make the assumption that the receiver is a list. Could
be anything...

[Lasse Reichstein Nielsen, 2015/09/08 11:38:03]

Good point, reworded.

     }
     return explanation;
   }