Make CSSPreloaderResourceClient hold weak references to its resource

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 2e50772cdedf25c2204dfc4214c549fca0f173a7..ea1841ac35bcc37c02960f148c1a1d296a2cec74 100644
--- a/third_party/WebKit/Source/core/html/parser/CSSPreloadScanner.cpp
+++ b/third_party/WebKit/Source/core/html/parser/CSSPreloadScanner.cpp
@@ -255,10 +255,9 @@ CSSPreloaderResourceClient::CSSPreloaderResourceClient(
     : m_policy(preloader->document()->settings()->cssExternalScannerPreload()
                    ? ScanAndPreload
                    : ScanOnly),
-      m_preloader(preloader) {
-  DCHECK(resource->getType() == Resource::Type::CSSStyleSheet);
-  setResource(toCSSStyleSheetResource(resource),
-              Resource::DontMarkAsReferenced);
+      m_preloader(preloader),
+      m_resource(toCSSStyleSheetResource(resource)) {

[Yoav Weiss, 2016/10/27 21:59:49]

Can you bring back the DCHECK? 

[Charlie Harrison, 2016/10/27 22:34:01]

AFAICT the to<Resource> type casts do this already (actually, they
ASSERT_WITH_SECURITY_IMPLICATION).

+  m_resource->addClient(this);
 }
 
 CSSPreloaderResourceClient::~CSSPreloaderResourceClient() {}
@@ -320,9 +319,16 @@ void CSSPreloaderResourceClient::fetchPreloads(PreloadRequestStream& preloads) {
   }
 }
 
+void CSSPreloaderResourceClient::clearResource() {
+  if (m_resource)
+    m_resource->removeClient(this);
+  m_resource.clear();
+}
+
 DEFINE_TRACE(CSSPreloaderResourceClient) {
   visitor->trace(m_preloader);
-  ResourceOwner<CSSStyleSheetResource>::trace(visitor);
+  visitor->trace(m_resource);
+  StyleSheetResourceClient::trace(visitor);
 }
 
 }  // namespace blink