Fixed #16744 -- Class based view should have the view object in the context

Updated the most recent patch from @claudep to apply again and updated
the documentation location.

docs/ref/class-based-views/mixins-simple.txt

@@ -17,8 +17,20 @@ ContextMixin
 
     .. method:: get_context_data(**kwargs)
 
-        Returns a dictionary representing the template context. The
-        keyword arguments provided will make up the returned context.
+        Returns a dictionary representing the template context. The keyword
+        arguments provided will make up the returned context.
+
+        The template context of all class-based generic views include a
+        ``view`` variable that points to the ``View`` instance.
+
+        .. admonition:: Use ``alters_data`` where appropriate
+
+            Note that having the view instance in the template context may
+            expose potentially hazardous methods to template authors.  To
+            prevent methods like this from being called in the template, set
+            ``alters_data=True`` on those methods.  For more information, read
+            the documentation on :ref:`rendering a template context
+            <alters-data-description>`.
 
 TemplateResponseMixin
 ---------------------