no need for a computed property

app/assets/javascripts/discourse/views/modal/upload_selector_view.js

@@ -20,15 +20,12 @@ Discourse.UploadSelectorView = Discourse.ModalBodyView.extend({
   }.property("controller.local"),
 
   hint: function() {
+    // cf. http://stackoverflow.com/a/9851769/11983
+    var isChrome = !!window.chrome && !(!!window.opera || navigator.userAgent.indexOf(' OPR/') >= 0);
     // chrome is the only browser that support copy & paste of images.
     return I18n.t("upload_selector.hint" + (this.get("isChrome") ? "_for_chrome" : ""));
   }.property(),
 
-  isChrome: function() {
-    // cf. http://stackoverflow.com/a/9851769/11983
-    return !!window.chrome && !(!!window.opera || navigator.userAgent.indexOf(' OPR/') >= 0);
-  }.property(),
-
   didInsertElement: function() {
     this._super();
     this.selectedChanged();