reverted:
--- b/core/themes/classy/templates/block--system-branding-block.html.twig
+++ /dev/null
@@ -1,32 +0,0 @@
-{% extends "@block/block.html.twig" %}
-{#
-/**
- * @file
- * Default theme implementation for a branding block.
- *
- * Each branding element variable (logo, name, slogan) is only available if
- * enabled in the block configuration.
- *
- * Available variables:
- * - site_logo: Logo for site as defined in Appearance or theme settings.
- * - site_name: Name for site as defined in Site information settings.
- * - site_slogan: Slogan for site as defined in Site information settings.
- *
- * @ingroup themeable
- */
-#}
-{% block content %}
-  {% if site_logo %}
-    <a href="{{ url('<front>') }}" title="{{ 'Home'|t }}" rel="home" class="site-logo">
-      <img src="{{ site_logo }}" alt="{{ 'Home'|t }}" />
-    </a>
-  {% endif %}
-  {% if site_name %}
-    <div class="site-name">
-      <a href="{{ url('<front>') }}" title="{{ 'Home'|t }}" rel="home">{{ site_name }}</a>
-    </div>
-  {% endif %}
-  {% if site_slogan %}
-    <div class="site-slogan">{{ site_slogan }}</div>
-  {% endif %}
-{% endblock %}
reverted:
--- b/core/themes/classy/templates/block--system-menu-block.html.twig
+++ /dev/null
@@ -1,65 +0,0 @@
-{#
-/**
- * @file
- * Default theme implementation for a menu block.
- *
- * Available variables:
- * - plugin_id: The ID of the block implementation.
- * - label: The configured label of the block if visible.
- * - configuration: A list of the block's configuration values.
- *   - label: The configured label for the block.
- *   - label_display: The display settings for the label.
- *   - module: The module that provided this block plugin.
- *   - cache: The cache settings.
- *   - Block plugin specific settings will also be stored here.
- * - block - The full block entity.
- *   - label_hidden: The hidden block title value if the block was
- *     configured to hide the title ('label' is empty in this case).
- *   - module: The module that generated the block.
- *   - delta: An ID for the block, unique within each module.
- *   - region: The block region embedding the current block.
- * - content: The content of this block.
- * - attributes: HTML attributes for the containing element.
- *   - id: A valid HTML ID and guaranteed unique.
- * - title_attributes: HTML attributes for the title element.
- * - content_attributes: HTML attributes for the content element.
- * - title_prefix: Additional output populated by modules, intended to be
- *   displayed in front of the main title tag that appears in the template.
- * - title_suffix: Additional output populated by modules, intended to be
- *   displayed after the main title tag that appears in the template.
- *
- * Headings should be used on navigation menus that consistently appear on
- * multiple pages. When this menu block's label is configured to not be
- * displayed, it is automatically made invisible using the 'visually-hidden' CSS
- * class, which still keeps it visible for screen-readers and assistive
- * technology. Headings allow screen-reader and keyboard only users to navigate
- * to or skip the links.
- * See http://juicystudio.com/article/screen-readers-display-none.php and
- * http://www.w3.org/TR/WCAG-TECHS/H42.html for more information.
- *
- * @ingroup themeable
- */
-#}
-{%
-  set classes = [
-    'block',
-    'block-menu',
-    'navigation',
-    'menu--' ~ derivative_plugin_id|clean_class,
-  ]
-%}
-{% set heading_id = attributes.id ~ '-menu'|clean_id %}
-<nav{{ attributes.addClass(classes) }} role="navigation" aria-labelledby="{{ heading_id }}">
-  {# Label. If not displayed, we still provide it for screen readers. #}
-  {% if not configuration.label_display %}
-    {% set title_attributes = title_attributes.addClass('visually-hidden') %}
-  {% endif %}
-  {{ title_prefix }}
-  <h2 id="{{ heading_id }}"{{ title_attributes }}>{{ configuration.label }}</h2>
-  {{ title_suffix }}
-
-  {# Menu. #}
-  {% block content %}
-    {{ content }}
-  {% endblock %}
-</nav>
reverted:
--- b/core/themes/classy/templates/breadcrumb.html.twig
+++ /dev/null
@@ -1,27 +0,0 @@
-{#
-/**
- * @file
- * Default theme implementation for a breadcrumb trail.
- *
- * Available variables:
- * - breadcrumb: Breadcrumb trail items.
- *
- * @ingroup themeable
- */
-#}
-{% if breadcrumb %}
-  <nav class="breadcrumb" role="navigation" aria-labelledby="system-breadcrumb">
-    <h2 id="system-breadcrumb" class="visually-hidden">{{ 'Breadcrumb'|t }}</h2>
-    <ol>
-    {% for item in breadcrumb %}
-      <li>
-        {% if item.url %}
-          <a href="{{ item.url }}">{{ item.text }}</a>
-        {% else %}
-          {{ item.text }}
-        {% endif %}
-      </li>
-    {% endfor %}
-    </ol>
-  </nav>
-{% endif %}
only in patch2:
unchanged:
--- a/core/modules/system/templates/block--system-menu-block.html.twig
+++ b/core/modules/system/templates/block--system-menu-block.html.twig
@@ -40,16 +40,8 @@
  * @ingroup themeable
  */
 #}
-{%
-  set classes = [
-    'block',
-    'block-menu',
-    'navigation',
-    'menu--' ~ derivative_plugin_id|clean_class,
-  ]
-%}
 {% set heading_id = attributes.id ~ '-menu'|clean_id %}
-<nav{{ attributes.addClass(classes) }} role="navigation" aria-labelledby="{{ heading_id }}">
+<nav role="navigation" aria-labelledby="{{ heading_id }}">
   {# Label. If not displayed, we still provide it for screen readers. #}
   {% if not configuration.label_display %}
     {% set title_attributes = title_attributes.addClass('visually-hidden') %}