Note: this list is generated by looking for the string for this theme hook, so it may include some references that are not actually using this theme hook.

backdrop_add_feed in core/includes/common.inc
Adds a feed URL for the current page.
backdrop_common_theme in core/includes/common.inc
Provides theme registration for themes across .inc files.
hook_block_view in core/modules/layout/layout.api.php
Return a rendered or renderable view of a block.
hook_theme in core/modules/system/system.api.php
Register a module (or theme's) theme implementations.
node_syndicate_content in core/modules/node/node.module
Returns a themed RSS icon which links to a provided feed.
template_preprocess_views_view in core/modules/views/templates/views.theme.inc
Preprocess the primary theme implementation for a view.
view::clone_view in core/modules/views/includes/view.inc
Safely clone a view.
views_plugin_style_rss::attach_to in core/modules/views/plugins/views_plugin_style_rss.inc