Set focus-related flags correctly after a server reload

(imported from commit 408469c0da0cfa5513e6838329816cd88665981f)

static/js/activity.js

@@ -17,7 +17,9 @@ var OFFLINE_THRESHOLD_SECS = 140;
 exports.ACTIVE = "active";
 exports.IDLE = "idle";
 
-exports.has_focus = true;
+// When you start Zulip, has_focus should be true, but it might not be the
+// case after a server-initiated reload.
+exports.has_focus = document.hasFocus && document.hasFocus();
 
 // We initialize this to true, to count new page loads, but set it to
 // false in the onload function in reload.js if this was a

static/js/notifications.js

@@ -3,7 +3,11 @@ var notifications = (function () {
 var exports = {};
 
 var notice_memory = {};
-var window_has_focus = true;
+
+// When you start Zulip, window_has_focus should be true, but it might not be the
+// case after a server-initiated reload.
+var window_has_focus = document.hasFocus && document.hasFocus();
+
 var asked_permission_already = false;
 var names;
 var supports_sound;

zerver/tests/frontend/node/activity.js

@@ -14,6 +14,12 @@ set_global('$', function () {
     };
 });
 
+set_global('document', {
+    hasFocus: function () {
+        return true;
+    }
+});
+
 var activity = require('js/activity.js');
 
 (function test_sort_users() {