Preload scan external CSS for @import

third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.cpp

Index: third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.cpp
diff --git a/third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.cpp b/third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.cpp
index 763015bfe8f64e39a326e59f580e92bb117b0d73..8946986691f97d8fbe73352c11e926be3ba66c6b 100644
--- a/third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.cpp
+++ b/third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.cpp
@@ -51,6 +51,7 @@ CSSStyleSheetResource* CSSStyleSheetResource::createForTest(const ResourceReques
 
 CSSStyleSheetResource::CSSStyleSheetResource(const ResourceRequest& resourceRequest, const ResourceLoaderOptions& options, const String& charset)
     : StyleSheetResource(resourceRequest, CSSStyleSheet, options, "text/css", charset)
+    , m_didNotifyFirstData(false)
 {
 }
 
@@ -80,8 +81,12 @@ void CSSStyleSheetResource::didAddClient(ResourceClient* c)
     // because setCSSStyleSheet() may cause scripts to be executed, which could destroy 'c' if it is an instance of HTMLLinkElement.
     // see the comment of HTMLLinkElement::setCSSStyleSheet.
     Resource::didAddClient(c);
+    if (m_didNotifyFirstData)
+        static_cast<StyleSheetResourceClient*>(c)->didAppendFirstData(this);
 
-    if (!isLoading())
+    // |c| might be removed in didAppendFirstData, so ensure it is still a
+    // client.
+    if (hasClient(c) && !isLoading())
         static_cast<StyleSheetResourceClient*>(c)->setCSSStyleSheet(resourceRequest().url(), response().url(), encoding(), this);
 }
 
@@ -97,6 +102,17 @@ const String CSSStyleSheetResource::sheetText(MIMETypeCheck mimeTypeCheck) const
     return decodedText();
 }
 
+void CSSStyleSheetResource::appendData(const char* data, size_t length)
+{
+    Resource::appendData(data, length);
+    if (m_didNotifyFirstData)
+        return;
+    ResourceClientWalker<StyleSheetResourceClient> w(clients());
+    while (StyleSheetResourceClient* c = w.next())
+        c->didAppendFirstData(this);
+    m_didNotifyFirstData = true;
+}
+
 void CSSStyleSheetResource::checkNotify()
 {
     // Decode the data to find out the encoding and keep the sheet text around during checkNotify()