`SkinMustache::getTemplateData()` is called twice causing a performance impact. When tested on `Special:UserLogin` or `Special:BlankPage`. The profiler output (for a single call) stated that this method takes over 25% of the execution time (217 ms). The method itself is pretty complex and builds a big array that is passed to Mustache, calling it twice adds unnecessary performance downgrade.
The first time is called in:
```
> SkinMustache::getTemplateData (/srv/mediawiki/php-1.42.0-wmf.5/includes/skins/SkinMustache.php)
> MediaWiki\Skins\Vector\SkinVector22::getTemplateData (/srv/mediawiki/php-1.42.0-wmf.5/skins/Vector/includes/SkinVector22.php)
> SkinMustache::generateHTML (/srv/mediawiki/php-1.42.0-wmf.5/includes/skins/SkinMustache.php)
> SkinTemplate::outputPage (/srv/mediawiki/php-1.42.0-wmf.5/includes/skins/SkinTemplate.php)
> MediaWiki\Output\OutputPage::output (/srv/mediawiki/php-1.42.0-wmf.5/includes/Output/OutputPage.php)
> MediaWiki::main (/srv/mediawiki/php-1.42.0-wmf.5/includes/MediaWiki.php)
> MediaWiki::run (/srv/mediawiki/php-1.42.0-wmf.5/includes/MediaWiki.php)
> wfIndexMain (/srv/mediawiki/php-1.42.0-wmf.5/index.php)
> /srv/mediawiki/php-1.42.0-wmf.5/index.php (/srv/mediawiki/php-1.42.0-wmf.5/index.php)
> /srv/mediawiki/w/index.php (/srv/mediawiki/w/index.php)
```
And then the second call comes from `SkinVector22:isTocAvailable`:
```
> MediaWiki\Skins\Vector\SkinVector22::isTocAvailable (/srv/mediawiki/php-1.42.0-wmf.5/skins/Vector/includes/SkinVector22.php)
> MediaWiki\Skins\Vector\SkinVector22::getTemplateData (/srv/mediawiki/php-1.42.0-wmf.5/skins/Vector/includes/SkinVector22.php)
> SkinMustache::generateHTML (/srv/mediawiki/php-1.42.0-wmf.5/includes/skins/SkinMustache.php)
> SkinTemplate::outputPage (/srv/mediawiki/php-1.42.0-wmf.5/includes/skins/SkinTemplate.php)
> MediaWiki\Output\OutputPage::output (/srv/mediawiki/php-1.42.0-wmf.5/includes/Output/OutputPage.php)
> MediaWiki::main (/srv/mediawiki/php-1.42.0-wmf.5/includes/MediaWiki.php)
> MediaWiki::run (/srv/mediawiki/php-1.42.0-wmf.5/includes/MediaWiki.php)
> wfIndexMain (/srv/mediawiki/php-1.42.0-wmf.5/index.php)
> /srv/mediawiki/php-1.42.0-wmf.5/index.php (/srv/mediawiki/php-1.42.0-wmf.5/index.php)
> /srv/mediawiki/w/index.php (/srv/mediawiki/w/index.php)
```
The first call to `getTemplateData` takes around 150ms, then the second call is a bit faster ~50ms due to caching -> but it happens within the same function, therefore there is no need to use call `parent::getTemplateData` once again. Thanks to this improvement we can shave off ~50ms per execution call.