MAGETWO-38010: Warnings During Running Static View Files Deployment Command

- added a test case for multi-line comment

Author: Olga Kopylova

lib/internal/Magento/Framework/Less/Test/Unit/PreProcessor/Instruction/ImportTest.php

@@ -91,13 +91,21 @@ public function processDataProvider()
                 'Magento_Module/something.css',
                 "@import (type) 'Magento_Module/something.css';",
             ],
-            'with commented lines' => [
+            'with single line comment' => [
                 '@import (type) "some/file.css" media;' . PHP_EOL
                     . '// @import (type) "unnecessary/file.css" media;',
                 'some/file.css',
                 'some/file.css',
                 "@import (type) 'some/file.css' media;" . PHP_EOL,
             ],
+            'with multi line comment' => [
+                '@import (type) "some/file.css" media;' . PHP_EOL
+                    . '/* @import (type) "unnecessary/file.css" media;' . PHP_EOL
+                    . '@import (type) "another/unnecessary/file.css" media; */',
+                'some/file.css',
+                'some/file.css',
+                "@import (type) 'some/file.css' media;" . PHP_EOL,
+            ],
         ];
     }