Fix popup dimensions to the viewport and show the close button

assets/css/src/modal.styl

@@ -45,7 +45,6 @@ body.mailpoet_modal_opened
   position: absolute
   z-index: 25
   top: 48px
-  padding-bottom: 48px
   margin: 0
 
 .mailpoet_popup_wrapper
@@ -54,6 +53,7 @@ body.mailpoet_modal_opened
   position: relative
   width: 100%
   z-index: 0
+  height: 96%
 
 .mailpoet_overlay_hidden .mailpoet_popup_wrapper
   border: 1px solid #333
@@ -75,6 +75,7 @@ body.mailpoet_modal_opened
 
 .mailpoet_popup_body
   padding: 10px 10px 10px 10px
+  height: 92%
 
 // modal panel
 #mailpoet_modal_overlay.mailpoet_panel_overlay

assets/css/src/newsletter_editor/libraryOverrides.styl

@@ -127,9 +127,6 @@ body
   background-color: $primary-background-color
   border: 1px solid $content-border-color
 
-#mailpoet_modal_close
-  display: none
-
 .wrap > .mailpoet_notice,
 .notice
 .update-nag

assets/js/src/newsletter_editor/components/sidebar.js

@@ -272,10 +272,13 @@ define([
         });
 
         var view = this.previewView.render();
-
+        this.previewView.$el.css('height', '100%');
+ 
         MailPoet.Modal.popup({
           template: '',
           element: this.previewView.$el,
+          width: '95%',
+          height: '94%',
           title: MailPoet.I18n.t('newsletterPreview'),
           onCancel: function() {
             this.previewView.destroy();
@@ -340,8 +343,10 @@ define([
     getTemplate: function() { return templates.newsletterPreview; },
     initialize: function(options) {
       this.previewUrl = options.previewUrl;
-      this.width = App.getConfig().get('newsletterPreview.width');
-      this.height = App.getConfig().get('newsletterPreview.height')
+      this.width = '100%';
+      this.height = '100%';
+      // this.width = App.getConfig().get('newsletterPreview.width');
+      // this.height = App.getConfig().get('newsletterPreview.height')
     },
     templateContext: function() {
       return {