Prefetch @import files from CSS files.

Source/core/html/HTMLLinkElement.h

Index: Source/core/html/HTMLLinkElement.h
diff --git a/Source/core/html/HTMLLinkElement.h b/Source/core/html/HTMLLinkElement.h
index 9e6048c7b88205eca09c231e59d6ea0665597f67..8643e2096740bc9c944b0041989fbd5c14ddbbd2 100644
--- a/Source/core/html/HTMLLinkElement.h
+++ b/Source/core/html/HTMLLinkElement.h
@@ -33,6 +33,10 @@
 #include "core/html/HTMLElement.h"
 #include "core/html/LinkRelAttribute.h"
 #include "core/html/LinkResource.h"
+#include "core/html/parser/BackgroundHTMLInputStream.h"
+#include "core/html/parser/CSSPreloadScanner.h"
+#include "core/html/parser/HTMLParserOptions.h"
+#include "core/html/parser/HTMLTokenizer.h"
 #include "core/loader/LinkLoader.h"
 #include "core/loader/LinkLoaderClient.h"
 
@@ -86,6 +90,7 @@ public:
 private:
     // From StyleSheetResourceClient
     virtual void setCSSStyleSheet(const String& href, const KURL& baseURL, const String& charset, const CSSStyleSheetResource*) override;
+    virtual void dataReceived(const CSSStyleSheetResource* cachedStyleSheet) override;
 
     enum DisabledState {
         Unset,
@@ -105,6 +110,12 @@ private:
     Document& document();
 
     RefPtrWillBeMember<CSSStyleSheet> m_sheet;
+    BackgroundHTMLInputStream m_input;
+    OwnPtr<HTMLToken> m_token;
+    HTMLParserOptions m_options;
+    OwnPtr<HTMLTokenizer> m_tokenizer;
+    OwnPtr<CSSPreloadScanner> m_preloadScanner;
+    unsigned m_preloadLength;
     DisabledState m_disabledState;
     PendingSheetType m_pendingSheetType;
     bool m_loading;