[+]: "reset css rules when new css is set" (revert the revert)

src/CssToInlineStyles.php

@@ -97,6 +97,12 @@ class CssToInlineStyles
    */
   private $excludeConditionalInlineStylesBlock = true;
 
+  /**
+   * Whether css was already processed and there's no need to do it again
+   * @var bool
+   */
+  private $isCssProcessed = false;
+
   /**
    * Exclude media queries from "$this->css" and keep media queries for inline-styles blocks
    *
@@ -141,6 +147,8 @@ public function setHTML($html)
   public function setCSS($css)
   {
     $this->css = (string)$css;
+
+    $this->isCssProcessed = false;
   }
 
   /**
@@ -189,7 +197,9 @@ public function convert($outputXHTML = false)
     }
 
     // process css
-    $this->processCSS();
+    if (!$this->isCssProcessed) {
+      $this->processCSS();
+    }
 
     // create new DOMDocument
     $document = $this->createDOMDocument();
@@ -343,6 +353,8 @@ private function processCSS()
     if (0 !== count($this->cssRules)) {
       usort($this->cssRules, array(__CLASS__, 'sortOnSpecificity'));
     }
+
+    $this->isCssProcessed = true;
   }
 
   /**