Avoid multiple calls and config fetch

Author: lbajsarowicz

Diff for: app/code/Magento/PageCache/Model/Config.php

@@ -121,7 +121,7 @@ public function __construct(
      */
     public function getType()
     {
-        return $this->_scopeConfig->getValue(self::XML_PAGECACHE_TYPE);
+        return (int)$this->_scopeConfig->getValue(self::XML_PAGECACHE_TYPE);
     }
 
     /**

Diff for: app/code/Magento/PageCache/Model/Layout/LayoutPlugin.php

@@ -74,10 +74,11 @@ public function afterGetOutput(Layout $subject, $result)
     {
         if ($subject->isCacheable() && $this->config->isEnabled()) {
             $tags = [[]];
+            $isVarnish = $this->config->getType() === Config::VARNISH;
+
             foreach ($subject->getAllBlocks() as $block) {
                 if ($block instanceof IdentityInterface) {
                     $isEsiBlock = $block->getTtl() > 0;
-                    $isVarnish = $this->config->getType() == Config::VARNISH;
                     if ($isVarnish && $isEsiBlock) {
                         continue;
                     }