The style context for MOZ_GTK_TEXT_VIEW is now created by copying from the widget instead of caching a widget and using its context.
No rendering changes are expected, unless themes are animating GtkTextView backgrounds.
In GTK 3.20, gtk_menu_item_draw() just draws the root widget gadget, depending on the theme to style menu items with CSS name "separator" appropriately.
This makes all relevant toolbars pick up the fact that the Windows accent color has changed and should check and if necessary update the "brighttext" property on them for styling of controls.
This is a bit of a hack-around to the fact that there is no real easy way otherwise to notify the front-end of color changes without needing a change in focus of the window.
There is a deliberate 300ms delay built in, because otherwise the styles might not have propagated yet, resulting in brighttext not being updated properly.
