Fix crash in CSSStyleSheetResource::appendData

third_party/WebKit/Source/core/html/parser/CSSPreloadScanner.cpp

Index: third_party/WebKit/Source/core/html/parser/CSSPreloadScanner.cpp
diff --git a/third_party/WebKit/Source/core/html/parser/CSSPreloadScanner.cpp b/third_party/WebKit/Source/core/html/parser/CSSPreloadScanner.cpp
index 19e8b68357cf27bd712ecd7bb63d734d2f68796a..1468d1184db505b830e4af45c737869b48909100 100644
--- a/third_party/WebKit/Source/core/html/parser/CSSPreloadScanner.cpp
+++ b/third_party/WebKit/Source/core/html/parser/CSSPreloadScanner.cpp
@@ -237,15 +237,15 @@ void CSSPreloadScanner::emitRule(const SegmentedString& source)
 }
 
 CSSPreloaderResourceClient::CSSPreloaderResourceClient(Resource* resource, HTMLResourcePreloader* preloader)
-    : m_resource(resource)
-    , m_preloader(preloader)
+    : m_preloader(preloader)
 {
+    ASSERT(resource->getType() == Resource::CSSStyleSheet);
+    setResource(static_cast<CSSStyleSheetResource*>(resource));
 }
 
 void CSSPreloaderResourceClient::notifyFinished(Resource* resource)
 {
-    resource->removeClient(this);
-    m_resource.clear();
+    clearResource();
 }
 
 // Only attach for one appendData call, as that's where most imports will likely
@@ -267,8 +267,13 @@ void CSSPreloaderResourceClient::didAppendFirstData(const CSSStyleSheetResource*
         DEFINE_STATIC_LOCAL(CustomCountHistogram, cssImportHistogram, ("PreloadScanner.ExternalCSS.PreloadCount", 1, 100, 50));
         cssImportHistogram.count(m_preloader->countPreloads() - currentPreloadCount);
     }
-    m_resource->removeClient(this);
-    m_resource.clear();
+    clearResource();
+}
+
+DEFINE_TRACE(CSSPreloaderResourceClient)
+{
+    visitor->trace(m_preloader);
+    ResourceOwner<StyleSheetResource>::trace(visitor);
 }
 
 } // namespace blink