remove pointer-events from titlebar if cursor is not over the toolbox

This allows the style to work with tabs_on_bottom.css without causing
tabs to appear when close to the top of the web-content, which would
make top ~36px inaccessible.

chrome/autohide_tabstoolbar.css

@@ -11,6 +11,11 @@ See the above repository for updates as well as full license text. */
   z-index: 1;
 }
 
+#navigator-toolbox:not(:hover) > #titlebar{
+  -moz-window-dragging: no-drag !important;
+  pointer-events: none
+}
+
 :root:not([customizing]) #navigator-toolbox:hover,
 :root:not([customizing]) #titlebar{
   margin-bottom: calc(0px - 2 * var(--tab-block-margin) - var(--tab-min-height));