MC-15763: Introduce critical CSS scope loaded through head

- Stabilization

Author: vzabaznov

app/code/Magento/Theme/Block/Html/Header/CriticalCss.php

@@ -53,10 +53,7 @@ public function getCriticalCssData()
             $asset = $this->assetRepo->createAsset($this->filePath, ['_secure' => 'false']);
             $content = $asset->getContent();
         } catch (NotFoundException $e) {
-            throw new LocalizedException(__(
-                'Cannot get critical css file data: "%1"',
-                $e->getMessage()
-            ));
+            $content = '';
         };
 
         return $content;

lib/internal/Magento/Framework/View/Page/Config/Reader/Head.php

@@ -34,7 +34,7 @@ class Head implements Layout\ReaderInterface
     /**#@-*/
 
     /**
-     * {@inheritdoc}
+     * @inheritdoc
      */
     public function getSupportedNodes()
     {
@@ -63,7 +63,9 @@ protected function addContentTypeByNodeName(Layout\Element $node)
     }
 
     /**
-     * {@inheritdoc}
+     * @param Layout\Reader\Context $readerContext
+     * @param Layout\Element $headElement
+     * @return $this|Layout\ReaderInterface
      */
     public function interpret(
         Layout\Reader\Context $readerContext,