Remove deprecated IllegalJSRegExpException class.

sdk/lib/core/exceptions.dart

Index: sdk/lib/core/exceptions.dart
diff --git a/sdk/lib/core/exceptions.dart b/sdk/lib/core/exceptions.dart
index 8ee78bcda9ad022203187fbd02b931c867a88076..800a6529ab209a109d82c40a115d020f15734e16 100644
--- a/sdk/lib/core/exceptions.dart
+++ b/sdk/lib/core/exceptions.dart
@@ -53,16 +53,6 @@ class FormatException implements Exception {
   String toString() => "FormatException: $message";
 }
 
-/**
- * Deprecated. Replaced by [FormatException].
- */
-@deprecated
-class IllegalJSRegExpException extends FormatException {
-  IllegalJSRegExpException(String pattern, String errmsg)
-      : super("Illegal pattern: $pattern, $errmsg");
-}
-
-
 class IntegerDivisionByZeroException implements Exception {
   const IntegerDivisionByZeroException();
   String toString() => "IntegerDivisionByZeroException";