Preload scan external css for @import

third_party/WebKit/Source/core/fetch/StyleSheetResourceClient.h

Index: third_party/WebKit/Source/core/fetch/StyleSheetResourceClient.h
diff --git a/third_party/WebKit/Source/core/fetch/StyleSheetResourceClient.h b/third_party/WebKit/Source/core/fetch/StyleSheetResourceClient.h
index 9656bd0f3d1088657e1e3282abc9cec24f410430..62c9475d06611cefe3a0c3b6543d49b81ae49d43 100644
--- a/third_party/WebKit/Source/core/fetch/StyleSheetResourceClient.h
+++ b/third_party/WebKit/Source/core/fetch/StyleSheetResourceClient.h
@@ -40,6 +40,10 @@ public:
     ResourceClientType getResourceClientType() const final { return StyleSheetType; }
     virtual void setCSSStyleSheet(const String& /* href */, const KURL& /* baseURL */, const String& /* charset */, const CSSStyleSheetResource*) {}
     virtual void setXSLStyleSheet(const String& /* href */, const KURL& /* baseURL */, const String& /* sheet */) {}
+
+    // This gets called on the very first appendData call for the
+    // CSSStyleSheetResource.
+    virtual void didAppendFirstData(const CSSStyleSheetResource*) {}
 };
 
 } // namespace blink