wp-includes/customize/class-wp-customize-theme-control.php:42Refresh the parameters passed to the JavaScript via JSON.
public function to_json() { parent::to_json(); $this->json['theme'] = $this->theme; }Introduced in 4.2.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/customize/class-wp-customize-theme-control.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.