Fix type of JavaException.cause.

pkg/analyzer/lib/src/generated/java_core.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library analyzer.src.generated.java_core;
 
 const int LONG_MAX_VALUE = 0x7fffffffffffffff;
 
 final Stopwatch nanoTimeStopwatch = new Stopwatch();
 
@@ skipping 232 matching lines @@
     int result = 1;
     for (var element in a) {
       result = 31 * result + (element == null ? 0 : element.hashCode);
     }
     return result;
   }
 }
 
 class JavaException implements Exception {
   final String message;
-  final Exception cause;
+  final Object cause;
   JavaException([this.message = "", this.cause = null]);
   JavaException.withCause(this.cause) : message = null;
   String toString() => "$runtimeType: $message $cause";
 }
 
 class JavaIOException extends JavaException {
   JavaIOException([message = "", cause = null]) : super(message, cause);
 }
 
 class JavaPatternMatcher {
@@ skipping 177 matching lines @@
 
 class UnsupportedOperationException extends JavaException {
   UnsupportedOperationException([message = ""]) : super(message);
 }
 
 class URISyntaxException implements Exception {
   final String message;
   URISyntaxException(this.message);
   String toString() => "URISyntaxException: $message";
 }