Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/CanvasElement.dartdoc

Index: lib/html/doc/interface/CanvasElement.dartdoc
diff --git a/lib/html/doc/interface/CanvasElement.dartdoc b/lib/html/doc/interface/CanvasElement.dartdoc
deleted file mode 100644
index 06d666a6c4b187a2bb5288b3e662b05728b2f800..0000000000000000000000000000000000000000
--- a/lib/html/doc/interface/CanvasElement.dartdoc
+++ /dev/null
@@ -1,25 +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 HTMLCanvasElement
-interface CanvasElement extends Element default _Elements {
-
-  CanvasElement([int height, int width]);
-
-  /** @domName HTMLCanvasElement.height */
-  int height;
-
-  /** @domName HTMLCanvasElement.width */
-  int width;
-
-  /** @domName HTMLCanvasElement.getContext */
-  Object getContext(String contextId);
-
-  /** @domName HTMLCanvasElement.toDataURL */
-  String toDataURL(String type);
-}