Revisions: force a scroll bar so that everything doesn't jerk around as you scrub due to the scroll bar popping in and out.

See #24425.

git-svn-id: https://develop.svn.wordpress.org/trunk@24688 602fd350-edb4-49c9-b593-d223f7449a82

wp-admin/css/wp-admin.css

@@ -3500,6 +3500,10 @@ td.plugin-title p {
 /*------------------------------------------------------------------------------
   11.2 - Post Revisions
 ------------------------------------------------------------------------------*/
+body.revision-php {
+	overflow-y: scroll; /* Force a scrollbar, so centering doesn't jump */
+}
+
 .revisions-control-frame,
 .revisions-diff-frame {
 	position: relative;