Use precaching for more data: urls than just images.

Source/core/fetch/RawResource.h

Index: Source/core/fetch/RawResource.h
diff --git a/Source/core/fetch/RawResource.h b/Source/core/fetch/RawResource.h
index 1dae4e65784d3cf59c40472d712ee3e4b03aa7a8..bb3546dbb053502bd75ceaefd3a3527cd41d0a0b 100644
--- a/Source/core/fetch/RawResource.h
+++ b/Source/core/fetch/RawResource.h
@@ -67,7 +67,6 @@ private:
             return new RawResource(request, m_type);
         }
     };
-    static void preCacheSubstituteDataForMainResource(const FetchRequest&, ResourceFetcher*, const SubstituteData&);
 
     void didAddClient(ResourceClient*) override;
     void appendData(const char*, unsigned) override;