WP_Customize_Themes_Panel
Customize Themes Panel Class
WordPress File wp-includes/customize/class-wp-customize-themes-panel.php
WP_Customize_Themes_Panel::content_template()
An Underscore (JS) template for this panel’s content (but not its container).
WP_Customize_Themes_Panel::render_template()
An Underscore (JS) template for rendering this panel’s container.