Reviewed by Chris Fleizach.

        [GTK] Implement ROLE_COMBO_BOX
        https://bugs.webkit.org/show_bug.cgi?id=25678

        Implement the remaining bits for combo boxes.

        This patch finishes the implementation, from the point of view of
        the Atk library, of those objects exposed to ATK as combo boxes,
        and their related elements (menus and menu items). It therefore
        implements the proper interfaces for each type of object related
        to combo boxes (AtkSelection for the combo box, AtkText for every
        menu item and AtkAction for the combo box, the menu and the menu
        items), takes care of emitting the proper signals when focus or a
        given a selection changes and adds a new unit test to check all
        this new stuff.

        Make possible to ask an AccessibleMenuListOption for a sensible
        string representation, so far only available through the private
        and MSAA related method nameForMSAA. Just moved the implementation
        of that method to an overriden version of stringValue(), which is
        platform independent, and called that from nameForMSAA().

        * accessibility/AccessibilityMenuListOption.h:
        * accessibility/AccessibilityMenuListOption.cpp:
        (WebCore::AccessibilityMenuListOption::nameForMSAA): Just call to
        stringValue(), which holds from now on that used to be here.
        (WebCore::AccessibilityMenuListOption::stringValue): New, override
        of AccessibilityObject::stringValue() to return a proper string.

        Emit the missing signals when a selection is made.

        * accessibility/gtk/AXObjectCacheAtk.cpp:
        (WebCore::AXObjectCache::postPlatformNotification): Emit the usual
        'focus' signals when a selection is made over the combo box.

        * accessibility/gtk/AccessibilityObjectWrapperAtk.cpp:
        (setAtkStateSetFromCoreObject): Ensure the EXPANDABLE and EXPANDED
        Atk states are added to the state set when needed.
        (listObjectForSelection): New, returns the proper list object (the
        one holding the list of available options as its children) for an
        specific AtkObject implementing AtkSelection. This is needed
        because sometimes the selectable options are not directly children
        of the AtkSelection object (i.e. a combo box has a 'menu' object
        as its only child of it, holding the list of options as children).
        (optionFromList): Use listObjectForSelection() to get the actual
        object holding the list of children as the available options.
        (optionFromSelection): Add support for combo boxes.
        (webkit_accessible_selection_add_selection): Ditto.
        (webkit_accessible_selection_clear_selection): Ditto.
        (webkit_accessible_selection_get_selection_count): Ditto.
        (webkit_accessible_selection_is_child_selected): Ditto.
        (webkit_accessible_selection_remove_selection): Ditto.
        (webkit_accessible_text_get_text): Makes sure stringValue() is
        considered to get the result substring when it was already
        considered when checking the maximum text length for the object.
        (getInterfaceMaskFromObject): Make sure the AtkSelection interface
        is implemented for the combo boxes, that the AtkText is
        implemented for the menu items and that the AtkAction interface is
        now implemented for every object (WebCore will decide what to do).

        Avoid a segfault crash when using this from unit tests.

        * platform/gtk/PopupMenuGtk.cpp:
        (WebCore::PopupMenuGtk::show): Make sure we got a valid GdkWindow
        before calling gdk_window_get_origin() over it.
2010-11-30  Mario Sanchez Prada  <msanchez@igalia.com>

        Reviewed by Chris Fleizach.

        [GTK] Implement ROLE_COMBO_BOX
        https://bugs.webkit.org/show_bug.cgi?id=25678

        New test to check the implementation of the combo boxes.

        * tests/testatk.c:
        (testWebkitAtkComboBox): New test, checking that the roles and the
        implemented interfaces for a combo box and its descendants work.
        (main): Added the new unit test.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@72958 268f45cc-cd09-0410-ab3c-d52691b4dbfc