Bug 1503272 - Hide the visibility of the titlebar when using lightweight themes with the Linux GTK theme. r=dao

This allows us to take advantage of the padding that the titlebar gets with the
-moz-window-titlebar / -moz-window-titlebar-maximized, but also allows us to
bypass the background texture applied to it.

We were doing this before, but it got removed in bug 1356920. Bug 1498356 was
originally landed as part of a more elaborate solution to this background texture
problem, and this patch makes bug 1498356 no longer necessary.

Differential Revision: https://phabricator.services.mozilla.com/D11429

--HG--
extra : moz-landing-system : lando

browser/themes/linux/browser.css

@@ -627,12 +627,19 @@ notification[value="translation"] menulist > .menulist-dropmarker {
     }
   }
 
-  :root[tabsintitlebar] > #navigator-toolbox > #titlebar:not(:-moz-lwtheme) {
+  :root[tabsintitlebar] > #navigator-toolbox > #titlebar {
     -moz-appearance: -moz-window-titlebar-maximized;
   }
-  :root[tabsintitlebar][sizemode="normal"] > #navigator-toolbox > #titlebar:not(:-moz-lwtheme) {
+  :root[tabsintitlebar][sizemode="normal"] > #navigator-toolbox > #titlebar {
     -moz-appearance: -moz-window-titlebar;
   }
+  :root[tabsintitlebar] > #navigator-toolbox > #titlebar:-moz-lwtheme {
+    visibility: hidden;
+  }
+  :root[tabsintitlebar] #toolbar-menubar:-moz-lwtheme,
+  :root[tabsintitlebar] #TabsToolbar:-moz-lwtheme {
+    visibility: visible;
+  }
 
   /* Add extra space to titlebar for dragging */
   :root[sizemode="normal"][chromehidden~="menubar"] #TabsToolbar,