Remove generated directories with 100s of files.

client/dom/generated/src/frog/XMLHttpRequest.dart

-
-class _XMLHttpRequestJs extends _EventTargetJs implements XMLHttpRequest native "*XMLHttpRequest" {
-
-  static final int DONE = 4;
-
-  static final int HEADERS_RECEIVED = 2;
-
-  static final int LOADING = 3;
-
-  static final int OPENED = 1;
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-  static final int UNSENT = 0;
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-  bool asBlob;
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-  final int readyState;
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-  final Object response;
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-  final _BlobJs responseBlob;
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-  final String responseText;
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-  String responseType;
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-  final _DocumentJs responseXML;
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-  final int status;
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-  final String statusText;
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-  final _XMLHttpRequestUploadJs upload;
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-  bool withCredentials;
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-  void abort() native;
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-  void addEventListener(String type, EventListener listener, [bool useCapture = null]) native;
-
-  bool dispatchEvent(_EventJs evt) native;
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-  String getAllResponseHeaders() native;
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-  String getResponseHeader(String header) native;
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-  void open(String method, String url, [bool async = null, String user = null, String password = null]) native;
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-  void overrideMimeType(String override) native;
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-  void removeEventListener(String type, EventListener listener, [bool useCapture = null]) native;
-
-  void send([var data = null]) native;
-
-  void setRequestHeader(String header, String value) native;
-}