diff --git a/core/includes/common.inc b/core/includes/common.inc
index dfd20fa..ed4a4d6 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -3658,73 +3658,85 @@ function drupal_render_page($page) {
 /**
  * Renders HTML given a structured array tree.
  *
- * Recursively iterates over each of the array elements, generating HTML code.
- *
- * Renderable arrays have two kinds of key/value pairs: properties and
- * children. Properties have keys starting with '#' and their values influence
- * how the array will be rendered. Children are all elements whose keys do not
- * start with a '#'. Their values should be renderable arrays themselves,
- * which will be rendered during the rendering of the parent array. The markup
- * provided by the children is typically inserted into the markup generated by
- * the parent array.
- *
- * HTML generation for a renderable array, and the treatment of any children,
- * is controlled by two properties containing theme functions, #theme and
- * #theme_wrappers.
- *
- * #theme is the theme function called first. If it is set and the element has
- * any children, it is the responsibility of the theme function to render
- * these children. For elements that are not allowed to have any children,
- * e.g. buttons or textfields, the theme function can be used to render the
- * element itself. If #theme is not present and the element has children, each
- * child is itself rendered by a call to drupal_render(), and the results are
- * concatenated.
- *
- * The #theme_wrappers property contains an array of theme functions which will
- * be called, in order, after #theme has run. These can be used to add further
- * markup around the rendered children; e.g., details add the required markup
- * for a details element around their rendered child elements. All wrapper theme
- * functions have to include the element's #children property in their output,
- * as it contains the output of the previous theme functions and the rendered
- * children.
- *
- * For example, for the form element type, by default only the #theme_wrappers
- * property is set, which adds the form markup around the rendered child
- * elements of the form. This allows you to set the #theme property on a
- * specific form to a custom theme function, giving you complete control over
- * the placement of the form's children while not at all having to deal with
- * the form markup itself.
- *
- * drupal_render() can optionally cache the rendered output of elements to
- * improve performance. To use drupal_render() caching, set the element's #cache
- * property to an associative array with one or several of the following keys:
- * - 'keys': An array of one or more keys that identify the element. If 'keys'
- *   is set, the cache ID is created automatically from these keys. See
- *   drupal_render_cid_create().
- * - 'granularity' (optional): Define the cache granularity using binary
- *   combinations of the cache granularity constants, e.g.
- *   DRUPAL_CACHE_PER_USER to cache for each user separately or
- *   DRUPAL_CACHE_PER_PAGE | DRUPAL_CACHE_PER_ROLE to cache separately for each
- *   page and role. If not specified the element is cached globally for each
- *   theme and language.
- * - 'cid': Specify the cache ID directly. Either 'keys' or 'cid' is required.
- *   If 'cid' is set, 'keys' and 'granularity' are ignored. Use only if you
- *   have special requirements.
- * - 'expire': Set to one of the cache lifetime constants.
- * - 'bin': Specify a cache bin to cache the element in. Defaults to 'cache'.
- *
- * This function is usually called from within another function, like
- * drupal_get_form() or a theme function. Elements are sorted internally
- * using uasort(). Since this is expensive, when passing already sorted
- * elements to drupal_render(), for example from a database query, set
- * $elements['#sorted'] = TRUE to avoid sorting them a second time.
- *
- * drupal_render() flags each element with a '#printed' status to indicate that
- * the element has been rendered, which allows individual elements of a given
- * array to be rendered independently and prevents them from being rendered
- * more than once on subsequent calls to drupal_render() (e.g., as part of a
- * larger array). If the same array or array element is passed more than once
- * to drupal_render(), it simply returns an empty string.
+ * Renderable arrays have two kinds of key/value pairs: properties and children.
+ * Properties have keys starting with '#' and their values influence how the
+ * array will be rendered. Children are all elements whose keys do not start
+ * with a '#'. Their values should be renderable arrays themselves, which will
+ * be rendered during the rendering of the parent array. The markup provided by
+ * the children is typically inserted into the markup generated by the parent
+ * array.
+ *
+ * The process of rendering an element is recursive unless the element defines
+ * an implemented theme hook in #theme. During each call to drupal_render(), the
+ * outermost renderable array (also known as an "element") is processed using
+ * the following steps:
+ *   - If this element has already been printed (#printed = TRUE) or the user
+ *     does not have access to it (#access = FALSE) then an empty string is
+ *     returned.
+ *   - If this element has #cache defined then the cached markup for this
+ *     element will be returned if it exists in drupal_render()'s cache. To use
+ *     drupal_render() caching, set the element's #cache property to an
+ *     associative array with one or several of the following keys:
+ *     - 'keys': An array of one or more keys that identify the element. If
+ *       'keys' is set, the cache ID is created automatically from these keys.
+ *       See drupal_render_cid_create().
+ *     - 'granularity' (optional): Define the cache granularity using binary
+ *       combinations of the cache granularity constants, e.g.
+ *       DRUPAL_CACHE_PER_USER to cache for each user separately or
+ *       DRUPAL_CACHE_PER_PAGE | DRUPAL_CACHE_PER_ROLE to cache separately for
+ *       each page and role. If not specified the element is cached globally for
+ *       each theme and language.
+ *     - 'cid': Specify the cache ID directly. Either 'keys' or 'cid' is
+ *       required. If 'cid' is set, 'keys' and 'granularity' are ignored. Use
+ *       only if you have special requirements.
+ *     - 'expire': Set to one of the cache lifetime constants.
+ *     - 'bin': Specify a cache bin to cache the element in. Default is 'cache'.
+ *   - If this element has #type defined and the default attributes for this
+ *     element have not already been merged in (#defaults_loaded = TRUE) then
+ *     the defaults for this type of element, defined in hook_element_info(),
+ *     are merged into the array. #defaults_loaded is set by functions that
+ *     process render arrays and call element_info() before passing the array to
+ *     drupal_render(), such as form_builder() in the Form API.
+ *   - If this element has an array of #pre_render functions defined, they are
+ *     called sequentially to modify the element before rendering. After all the
+ *     #pre_render functions have been called, #printed is checked a second time
+ *     in case a #pre_render function flags the element as printed.
+ *   - The child elements of this element are sorted by weight using uasort() in
+ *     element_children(). Since this is expensive, when passing already sorted
+ *     elements to drupal_render(), for example from a database query, set
+ *     $elements['#sorted'] = TRUE to avoid sorting them a second time.
+ *   - The main render phase to produce #children for this element takes place:
+ *     - If this element has #theme defined and #theme is an implemented theme
+ *       hook/suggestion then theme() is called and must render both the element
+ *       and its children. If #render_children is set, theme() will not be
+ *       called. #render_children is usually only set internally by theme() so
+ *       that we can avoid the situation where drupal_render() called from
+ *       within a theme preprocess function creates an infinite loop.
+ *     - If this element does not have a defined #theme, or the defined #theme
+ *       hook is not implemented, or #render_children is set, then
+ *       drupal_render() is called recursively on each of the child elements of
+ *       this element and the result of each is concatenated onto #children.
+ *       This is skipped if #children is not empty at this point.
+ *     - Once #children has been rendered for this element, if #theme is not
+ *       implemented and #markup is set for this element, #markup will be
+ *       prepended to #children.
+ *   - Any additional JavaScript, CSS or custom data is added to this element.
+ *   - If this element has an array of #theme_wrappers defined and
+ *     #render_children is not set, #children is then re-rendered by passing the
+ *     element in its current state to theme() successively for each item in
+ *     #theme_wrappers.
+ *   - If this element has an array of #post_render functions defined, they are
+ *     called sequentially to modify the rendered #children. Unlike #pre_render
+ *     functions, #post_render functions are passed both the rendered #children
+ *     attribute as a string and the element itself.
+ *   - If this element has #prefix and/or #suffix defined, they are concatenated
+ *     to #children.
+ *   - If this element has #cache defined, the rendered output of this element
+ *     is saved to drupal_render()'s internal cache.
+ *   - #printed is set to TRUE for this element to ensure that it is only
+ *     rendered once.
+ *   - The final value of #children for this element is returned as the rendered
+ *     output.
  *
  * @param array $elements
  *   The structured array describing the data to be rendered.