UX: on mobile devices iOS or Android always use full screen login

This simplifies life for users and embedded browsers and works around
all popup blocking.

There is no point to popup tabs on Android or iOS, it just causes
confusion.

app/assets/javascripts/discourse/controllers/login.js.es6

@@ -176,7 +176,7 @@ export default Ember.Controller.extend(ModalFunctionality, {
 
   authMessage: (function() {
     if (Ember.isEmpty(this.get('authenticate'))) return "";
-    const method = findAll(this.siteSettings).findProperty("name", this.get("authenticate"));
+    const method = findAll(this.siteSettings, this.capabilities, this.isMobileDevice).findProperty("name", this.get("authenticate"));
     if(method){
       return method.get('message');
     }

app/assets/javascripts/discourse/models/login-method.js.es6

@@ -22,7 +22,7 @@ const LoginMethod = Ember.Object.extend({
 let methods;
 let preRegister;
 
-export function findAll(siteSettings) {
+export function findAll(siteSettings, capabilities, isMobileDevice) {
   if (methods) { return methods; }
 
   methods = [];
@@ -55,6 +55,12 @@ export function findAll(siteSettings) {
     });
     preRegister = undefined;
   }
+
+  // On Mobile, Android or iOS always go with full screen
+  if (isMobileDevice || capabilities.isIOS || capabilities.isAndroid) {
+    methods.forEach(m=>m.set("fullScreenLogin", true));
+  }
+
   return methods;
 }
 

app/assets/javascripts/discourse/routes/application.js.es6

@@ -204,7 +204,11 @@ const ApplicationRoute = Discourse.Route.extend(OpenComposer, {
   },
 
   _autoLogin(modal, modalClass, notAuto) {
-    const methods = findAll(this.siteSettings);
+
+    const methods = findAll(this.siteSettings,
+                            this.container.lookup('capabilities:main'),
+                            this.site.isMobileDevice);
+
     if (!this.siteSettings.enable_local_logins && methods.length === 1) {
       this.controllerFor('login').send('externalLogin', methods[0]);
     } else {