Preload scan external css for @import

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

Index: third_party/WebKit/Source/core/html/parser/CSSPreloadScanner.h
diff --git a/third_party/WebKit/Source/core/html/parser/CSSPreloadScanner.h b/third_party/WebKit/Source/core/html/parser/CSSPreloadScanner.h
index b56ef885e8301e0609db0e85ab6ab34b236d835f..9abe1ae1e365522df23b4073fd1ecaf4dd66b795 100644
--- a/third_party/WebKit/Source/core/html/parser/CSSPreloadScanner.h
+++ b/third_party/WebKit/Source/core/html/parser/CSSPreloadScanner.h
@@ -27,13 +27,15 @@
 #ifndef CSSPreloadScanner_h
 #define CSSPreloadScanner_h
 
-#include "core/html/parser/HTMLResourcePreloader.h"
+#include "core/fetch/StyleSheetResourceClient.h"
 #include "core/html/parser/HTMLToken.h"
+#include "core/html/parser/PreloadRequest.h"
 #include "wtf/text/StringBuilder.h"
 
 namespace blink {
 
 class SegmentedString;
+class HTMLResourcePreloader;
 
 class CSSPreloadScanner {
     DISALLOW_NEW();
@@ -80,6 +82,22 @@ private:
     const KURL* m_predictedBaseElementURL = nullptr;
 };
 
+// Each CSSPreloaderResourceClient keeps track of a single CSS resource, and
+// drives a CSSPreloadScanner as raw data arrives for it. This lets us preload
+// @import tags before parsing.
+class CSSPreloaderResourceClient : public StyleSheetResourceClient {
+public:
+    CSSPreloaderResourceClient(HTMLResourcePreloader*);
+    void didAppendData(const CSSStyleSheetResource*) override;
+    String debugName() const override { return "CSSPreloaderResourceClient"; }
+
+private:
+    void preloadChunk(const String& chunk, const CSSStyleSheetResource*);
+    CSSPreloadScanner m_cssPreloadScanner;
+    RawPtrWillBeWeakPersistent<HTMLResourcePreloader> m_preloader;
+    size_t m_streamPosition;
+};
+
 } // namespace blink
 
 #endif