Ticket #29485: 29485.2.diff

src/wp-admin/js/editor-expand.js

@@ -195 +195 @@
                                 return;
                         }
 
+                        // Bail on pageup/pagedown/home/end.
+                        if ( key >= 33 && key <= 36 ) {
+                                return;
+                        }
+
                         cursorTop = offset.top + editor.iframeElement.getBoundingClientRect().top;
                         cursorBottom = cursorTop + offset.height;
                         cursorTop = cursorTop - buffer;