[AIRFLOW-6733] Extend not replace template (apache#7366)

cherry-picked from 220bc0e

airflow/www_rbac/app.py

@@ -103,7 +103,7 @@ def create_app(config=None, session=None, testing=False, app_name="Airflow"):
             app,
             db.session if not session else session,
             security_manager_class=security_manager_class,
-            base_template='appbuilder/baselayout.html',
+            base_template='airflow/master.html',
             update_perms=conf.getboolean('webserver', 'UPDATE_FAB_PERMS'))
 
         def init_views(appbuilder):

airflow/www_rbac/templates/airflow/master.html

@@ -15,4 +15,51 @@
   limitations under the License.
 
 #}
-{% extends "appbuilder/baselayout.html" %}
+
+{% extends 'appbuilder/baselayout.html' %}
+
+{% block head_css %}
+  {{ super() }}
+
+  {% if not appbuilder.app_theme %}
+    {# airflowDefaultTheme.css file contains the styles from local bootstrap-theme.css #}
+    <link href="{{ url_for_asset('airflowDefaultTheme.css') }}" rel="stylesheet">
+  {% endif %}
+  <link href="{{ url_for_asset('main.css') }}" rel="stylesheet">
+
+  <link rel="icon" type="image/png" href="{{ url_for('static', filename='pin_32.png') }}">
+{% endblock %}
+
+
+{% block messages %}
+  {% include 'appbuilder/flash.html' %}
+  {% if scheduler_job is defined and (not scheduler_job or not scheduler_job.is_alive()) %}
+    <div class="alert alert-warning">
+      <p>The scheduler does not appear to be running.
+      {% if scheduler_job %}
+      Last heartbeat was received <time title="{{ scheduler_job.latest_heartbeat.isoformat() }}" datetime="{{ scheduler_job.latest_heartbeat.isoformat() }}">{{ macros.datetime_diff_for_humans(scheduler_job.latest_heartbeat) }}</time>.
+      {% endif %}
+      </p>
+      <p>The DAGs list may not update, and new tasks will not be scheduled.</p>
+    </div>
+  {% endif %}
+{% endblock %}
+
+{% block tail_js %}
+  {{ super() }}
+
+  <script type="text/javascript">
+    // below variables are used in base.js
+    var hostName = '{{ hostname }}';
+    var csrfToken = '{{ csrf_token() }}';
+    $("time[title]").tooltip()
+  </script>
+  <!--[if IE ]>
+  <script src="{{ url_for_asset('ie.js') }}" type="text/javascript"></script>
+  <![endif]-->
+  <script src="{{ url_for_asset('base.js') }}" type="text/javascript"></script>
+
+  {% if analytics_tool is defined and analytics_tool %}
+    {% include "analytics/" + analytics_tool + ".html" %}
+  {% endif %}
+{% endblock %}