The title that should be displayed on the page.
The page title can come from a number of places: copied from a block, a menu callback (within the main page content block), or a custom layout title. We track this separately from backdrop_set_title() to avoid double- setting or getting the title within a single request.
This value is not escaped and should be run through check_plain() when adding to the page. The title should already be translated when set.
modules/ layout/ plugins/ renderers/ layout_renderer_standard.inc, line 135
- The standard render for a Layout display object.
protected $page_title = NULL;