/usr/share/idl/thunderbird/calIWcapSession.idl is in thunderbird-dev 1:52.8.0-1~deb8u1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 | /* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "nsISupports.idl"
interface calIWcapCalendar;
interface nsIURI;
/**
 * WCAP session.
 */
[scriptable, uuid(477B4534-C297-40a1-ADF2-5A7E2A81816A)]
interface calIWcapSession : nsISupports
{
    /**
     * Setting this URI causes the session to logged out and disconnected.
     */
    attribute nsIURI uri;
    /**
     * User that has established this session.
     * @exception NS_ERROR_NOT_AVAILABLE if not logged in
     */
    readonly attribute string userId;
    /**
     * Determines whether the user is currentl logged in.
     * Does _not_ check whether the user's ticket has timed out!
     */
    readonly attribute boolean isLoggedIn;
    /**
     * Gets the default calendar instance of this session.
     */
    readonly attribute calIWcapCalendar defaultCalendar;
};
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