Information about full_header and context_header has been added to
upgrade.txt.
* Themes Bootstrapbase, Clean and More have undergone some changes for RTL layouts see - MDL-48160.
* Themes Clean amd More page header background logo, if loaded, no longer links to the home page.
+* Themes Clean and More have been updated to use the renderer full_header(). This renderer (when in a user context) displays a message button
+ and consequently the link to message users have been removed from various pages. It is recommended that theme developers use this
+ renderer to ensure that they do not suffer from a reduction in access to this feature.
+* $OUTPUT->context_header() has been introduced to produce headers similar to what full_header() creates. This renderer is used for creating
+ subsequent headers in a page. If provided with user information, this render will also display a message button like full_header().
=== 2.8 ===