feat: [FC-0070] add events and style for rendering Split xblock in chromeless template (#35813)

This feature introduces functionalities to improve XBlock interactions within iframes:

  * Add styles that adopt default styles for Split Test which renders chromless template via iframe in MFE Authoring.
  * When the isIframeEmbed option is enabled, the XBlock sends a postMessage to the parent window. When sending such a message, the standard link transition is cancelled and the transition is carried out in MFE Authoring.

cms/djangoapps/contentstore/helpers.py

@@ -82,6 +82,22 @@ def is_unit(xblock, parent_xblock=None):
     return False
 
 
+def is_library_content(xblock):
+    """
+    Returns true if the specified xblock is library content.
+    """
+    return xblock.category == 'library_content'
+
+
+def get_parent_if_split_test(xblock):
+    """
+    Returns the parent of the specified xblock if it is a split test, otherwise returns None.
+    """
+    parent_xblock = get_parent_xblock(xblock)
+    if parent_xblock and parent_xblock.category == 'split_test':
+        return parent_xblock
+
+
 def xblock_has_own_studio_page(xblock, parent_xblock=None):
     """
     Returns true if the specified xblock has an associated Studio page. Most xblocks do

cms/djangoapps/contentstore/views/component.py

@@ -25,7 +25,11 @@ from common.djangoapps.edxmako.shortcuts import render_to_response
 from common.djangoapps.student.auth import has_course_author_access
 from common.djangoapps.xblock_django.api import authorable_xblocks, disabled_xblocks
 from common.djangoapps.xblock_django.models import XBlockStudioConfigurationFlag
-from cms.djangoapps.contentstore.helpers import is_unit
+from cms.djangoapps.contentstore.helpers import (
+    get_parent_if_split_test,
+    is_unit,
+    is_library_content,
+)
 from cms.djangoapps.contentstore.toggles import (
     libraries_v1_enabled,
     libraries_v2_enabled,
@@ -148,11 +152,12 @@ def container_handler(request, usage_key_string):  # pylint: disable=too-many-st
             except ItemNotFoundError:
                 return HttpResponseBadRequest()
 
-            is_unit_page = is_unit(xblock)
-            unit = xblock if is_unit_page else None
+            if use_new_unit_page(course.id):
+                if is_unit(xblock) or is_library_content(xblock):
+                    return redirect(get_unit_url(course.id, xblock.location))
 
-            if is_unit_page and use_new_unit_page(course.id):
-                return redirect(get_unit_url(course.id, unit.location))
+                if split_xblock := get_parent_if_split_test(xblock):
+                    return redirect(get_unit_url(course.id, split_xblock.location))
 
             container_handler_context = get_container_handler_context(request, usage_key, course, xblock)
             container_handler_context.update({

cms/djangoapps/contentstore/xblock_storage_handlers/view_handlers.py

@@ -611,6 +611,7 @@ def _create_block(request):
         modulestore().update_item(created_block, request.user.id)
         response["upstreamRef"] = upstream_ref
         response["static_file_notices"] = asdict(static_file_notices)
+        response["parent_locator"] = parent_locator
 
     return JsonResponse(response)