Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/ButtonElement.dartdoc

Index: lib/html/doc/interface/ButtonElement.dartdoc
diff --git a/lib/html/doc/interface/ButtonElement.dartdoc b/lib/html/doc/interface/ButtonElement.dartdoc
deleted file mode 100644
index 2945c689410dc0e78838ea6e2c3ba7a7c6255ce3..0000000000000000000000000000000000000000
--- a/lib/html/doc/interface/ButtonElement.dartdoc
+++ /dev/null
@@ -1,64 +0,0 @@
-// Copyright (c) 2012, 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.
-
-// WARNING:
-//   This file contains documentation that is merged into the real source.
-//   Do not make code changes here.
-
-/// @domName HTMLButtonElement
-interface ButtonElement extends Element default _Elements {
-
-  ButtonElement();
-
-  /** @domName HTMLButtonElement.autofocus */
-  bool autofocus;
-
-  /** @domName HTMLButtonElement.disabled */
-  bool disabled;
-
-  /** @domName HTMLButtonElement.form */
-  final FormElement form;
-
-  /** @domName HTMLButtonElement.formAction */
-  String formAction;
-
-  /** @domName HTMLButtonElement.formEnctype */
-  String formEnctype;
-
-  /** @domName HTMLButtonElement.formMethod */
-  String formMethod;
-
-  /** @domName HTMLButtonElement.formNoValidate */
-  bool formNoValidate;
-
-  /** @domName HTMLButtonElement.formTarget */
-  String formTarget;
-
-  /** @domName HTMLButtonElement.labels */
-  final NodeList labels;
-
-  /** @domName HTMLButtonElement.name */
-  String name;
-
-  /** @domName HTMLButtonElement.type */
-  final String type;
-
-  /** @domName HTMLButtonElement.validationMessage */
-  final String validationMessage;
-
-  /** @domName HTMLButtonElement.validity */
-  final ValidityState validity;
-
-  /** @domName HTMLButtonElement.value */
-  String value;
-
-  /** @domName HTMLButtonElement.willValidate */
-  final bool willValidate;
-
-  /** @domName HTMLButtonElement.checkValidity */
-  bool checkValidity();
-
-  /** @domName HTMLButtonElement.setCustomValidity */
-  void setCustomValidity(String error);
-}