FEATURE: Allow overriding text size from a different device (#6955)

This brings the feature in line with the theme selection system

app/assets/javascripts/discourse/controllers/preferences/interface.js.es6

@@ -126,13 +126,8 @@ export default Ember.Controller.extend(PreferencesTabController, {
               this.get("model.user_option.theme_key_seq")
             );
           }
-          if (
-            makeTextSizeDefault ||
-            this.get("model.user_option.text_size") === $.cookie("text_size")
-          ) {
-            $.removeCookie("text_size");
-          } else {
-            $.cookie("text_size", this.get("textSize"));
+          if (!makeTextSizeDefault) {
+            this.get("model").updateTextSizeCookie(this.get("textSize"));
           }
 
           this.homeChanged();

app/assets/javascripts/discourse/models/user.js.es6

@@ -705,6 +705,25 @@ const User = RestModel.extend({
     });
 
     return _.uniq(titles).sort();
+  },
+
+  @computed("user_option.text_size_seq", "user_option.text_size")
+  currentTextSize(serverSeq, serverSize) {
+    if ($.cookie("text_size")) {
+      const [cookieSize, cookieSeq] = $.cookie("text_size").split("|");
+      if (cookieSeq >= serverSeq) {
+        return cookieSize;
+      }
+    }
+    return serverSize;
+  },
+
+  updateTextSizeCookie(newSize) {
+    const seq = this.get("user_option.text_size_seq");
+    $.cookie("text_size", `${newSize}|${seq}`, {
+      path: "/",
+      expires: 9999
+    });
   }
 });
 

app/assets/javascripts/discourse/routes/preferences-interface.js.es6

@@ -4,10 +4,9 @@ export default RestrictedUserRoute.extend({
   showFooter: true,
 
   setupController(controller, user) {
-    const textSize = $.cookie("text_size") || user.get("user_option.text_size");
     controller.setProperties({
       model: user,
-      textSize
+      textSize: user.get("currentTextSize")
     });
   }
 });