Prefetch @import files from CSS files.

Source/core/fetch/CSSStyleSheetResource.cpp

Index: Source/core/fetch/CSSStyleSheetResource.cpp
diff --git a/Source/core/fetch/CSSStyleSheetResource.cpp b/Source/core/fetch/CSSStyleSheetResource.cpp
index 869d7ca543715dce7f4a7c78d1f82958ea7da477..bdcd3152b31ab2aff9050c07b43e92ea1b3b283b 100644
--- a/Source/core/fetch/CSSStyleSheetResource.cpp
+++ b/Source/core/fetch/CSSStyleSheetResource.cpp
@@ -109,6 +109,16 @@ void CSSStyleSheetResource::checkNotify()
     m_decodedSheetText = String();
 }
 
+void CSSStyleSheetResource::appendData(const char* data, unsigned length)
+{
+    Resource::appendData(data, length);
+
+    ResourcePtr<CSSStyleSheetResource> protect(this);
+    ResourceClientWalker<StyleSheetResourceClient> walker(m_clients);
+    while (StyleSheetResourceClient* client = walker.next())
+        client->dataReceived(this);
+}
+
 bool CSSStyleSheetResource::isSafeToUnlock() const
 {
     return m_data->hasOneRef();