Close info bar when clicking on it

issue9621
review318281002

src/sao.less

@@ -26,6 +26,23 @@ html[theme="default"] {
   .col(1); // kickstart it
 }
 
+// Backport from Bootstrap 4
+.stretched-link {
+    &::after {
+        position: absolute;
+        top: 0;
+        right: 0;
+        bottom: 0;
+        left: 0;
+        z-index: 1;
+        // Just in case `pointer-events: none` is set on a parent
+        pointer-events: auto;
+        content: "";
+        // IE10 bugfix, see https://stackoverflow.com/questions/16947967/ie10-hover-pseudo-class-doesnt-work-without-background-color
+        background-color: rgba(0, 0, 0, 0);
+    }
+}
+
 
 .navbar-inverse {
     .close {

src/window.js

@@ -61,7 +61,7 @@
                 'role': 'alert'
             }).append(jQuery('<button/>', {
                 'type': 'button',
-                'class': 'close',
+                'class': 'close stretched-link',
                 'aria-label': Sao.i18n.gettext('Close')
             }).append(jQuery('<span/>', {
                 'aria-hidden': true