Add missing null check in PageSerializer::serializeCSSStyleSheet()

Source/core/page/PageSerializer.cpp

Index: Source/core/page/PageSerializer.cpp
diff --git a/Source/core/page/PageSerializer.cpp b/Source/core/page/PageSerializer.cpp
index 31549449cf3cdf357dd93512cc09a9bae731148d..d9c503590cc4b43184d401e4073e33c41069c0dd 100644
--- a/Source/core/page/PageSerializer.cpp
+++ b/Source/core/page/PageSerializer.cpp
@@ -242,13 +242,13 @@ void PageSerializer::serializeFrame(LocalFrame* frame)
             HTMLLinkElement& linkElement = toHTMLLinkElement(element);
             if (CSSStyleSheet* sheet = linkElement.sheet()) {
                 KURL url = document.completeURL(linkElement.getAttribute(HTMLNames::hrefAttr));
-                serializeCSSStyleSheet(sheet, url);
+                serializeCSSStyleSheet(*sheet, url);
                 ASSERT(m_resourceURLs.contains(url));
             }
         } else if (isHTMLStyleElement(element)) {
             HTMLStyleElement& styleElement = toHTMLStyleElement(element);
             if (CSSStyleSheet* sheet = styleElement.sheet())
-                serializeCSSStyleSheet(sheet, KURL());
+                serializeCSSStyleSheet(*sheet, KURL());
         }
     }
 
@@ -258,26 +258,27 @@ void PageSerializer::serializeFrame(LocalFrame* frame)
     }
 }
 
-void PageSerializer::serializeCSSStyleSheet(CSSStyleSheet* styleSheet, const KURL& url)
+void PageSerializer::serializeCSSStyleSheet(CSSStyleSheet& styleSheet, const KURL& url)
 {
     StringBuilder cssText;
-    for (unsigned i = 0; i < styleSheet->length(); ++i) {
-        CSSRule* rule = styleSheet->item(i);
+    for (unsigned i = 0; i < styleSheet.length(); ++i) {
+        CSSRule* rule = styleSheet.item(i);
         String itemText = rule->cssText();
         if (!itemText.isEmpty()) {
             cssText.append(itemText);
-            if (i < styleSheet->length() - 1)
+            if (i < styleSheet.length() - 1)
                 cssText.append("\n\n");
         }
-        ASSERT(styleSheet->ownerDocument());
-        Document& document = *styleSheet->ownerDocument();
+        ASSERT(styleSheet.ownerDocument());
+        Document& document = *styleSheet.ownerDocument();
         // Some rules have resources associated with them that we need to retrieve.
         if (rule->type() == CSSRule::IMPORT_RULE) {
             CSSImportRule* importRule = toCSSImportRule(rule);
             KURL importURL = document.completeURL(importRule->href());
             if (m_resourceURLs.contains(importURL))
                 continue;
-            serializeCSSStyleSheet(importRule->styleSheet(), importURL);
+            if (importRule->styleSheet())
+                serializeCSSStyleSheet(*importRule->styleSheet(), importURL);
         } else if (rule->type() == CSSRule::FONT_FACE_RULE) {
             retrieveResourcesForProperties(&toCSSFontFaceRule(rule)->styleRule()->properties(), document);
         } else if (rule->type() == CSSRule::STYLE_RULE) {
@@ -287,7 +288,7 @@ void PageSerializer::serializeCSSStyleSheet(CSSStyleSheet* styleSheet, const KUR
 
     if (url.isValid() && !m_resourceURLs.contains(url)) {
         // FIXME: We should check whether a charset has been specified and if none was found add one.
-        WTF::TextEncoding textEncoding(styleSheet->contents()->charset());
+        WTF::TextEncoding textEncoding(styleSheet.contents()->charset());
         ASSERT(textEncoding.isValid());
         String textString = cssText.toString();
         CString text = textEncoding.normalizeAndEncode(textString, WTF::EntitiesForUnencodables);