Use `gl.utils.isMetaClick` to identify meta-clicks

app/assets/javascripts/merge_request_tabs.js.es6

@@ -104,11 +104,7 @@ require('./flash');
     clickTab(e) {
       if (e.target) {
         const targetLink = e.target.getAttribute('href');
-        // Allow following special clicks to make link open in new tab
-        // 1) Cmd + Click on Mac (e.metaKey)
-        // 2) Ctrl + Click on PC (e.ctrlKey)
-        // 3) Middle-click or Mouse Wheel Click (e.which is 2)
-        if (e.metaKey || e.ctrlKey || e.which === 2) {
+        if (gl.utils.isMetaClick(e)) {
           e.stopImmediatePropagation();
           window.open(targetLink, '_blank');
         }

app/assets/javascripts/todos.js.es6

@@ -157,11 +157,7 @@
         return;
       }
 
-      // Allow following special clicks to make link open in new tab
-      // 1) Cmd + Click on Mac (e.metaKey)
-      // 2) Ctrl + Click on PC (e.ctrlKey)
-      // 3) Middle-click or Mouse Wheel Click (e.which is 2)
-      if (e.metaKey || e.ctrlKey || e.which === 2) {
+      if (gl.utils.isMetaClick(e)) {
         e.preventDefault();
         // Meta-Click on username leads to different URL than todoLink.
         // Turbolinks can resolve that URL, but window.open requires URL manually.