Prefetch @import files from CSS files.

Source/core/html/HTMLLinkElement.cpp

Index: Source/core/html/HTMLLinkElement.cpp
diff --git a/Source/core/html/HTMLLinkElement.cpp b/Source/core/html/HTMLLinkElement.cpp
index fbb7a1a97986d7c41135cd2e37e4d288f299d37b..3aec952231469c05250df7dd17f572f4fd653d52 100644
--- a/Source/core/html/HTMLLinkElement.cpp
+++ b/Source/core/html/HTMLLinkElement.cpp
@@ -44,8 +44,10 @@
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/html/imports/LinkImport.h"
+#include "core/html/parser/CSSPreloadScanner.h"
 #include "core/loader/FrameLoader.h"
 #include "core/loader/FrameLoaderClient.h"
+#include "platform/text/SegmentedString.h"
 #include "wtf/StdLibExtras.h"
 
 namespace WebCore {
@@ -369,6 +371,7 @@ LinkStyle::LinkStyle(HTMLLinkElement* owner)
     , m_loading(false)
     , m_firedLoad(false)
     , m_loadedSheet(false)
+    , m_isPreloadScanning(true)
 {
 }
 
@@ -428,6 +431,19 @@ void LinkStyle::setCSSStyleSheet(const String& href, const KURL& baseURL, const
         const_cast<CSSStyleSheetResource*>(cachedStyleSheet)->saveParsedStyleSheet(styleSheet);
 }
 
+void LinkStyle::dataReceived(const CSSStyleSheetResource* cachedStyleSheet, const char* data, int length)
+{
+    if (m_isPreloadScanning) {
+        m_isPreloadScanning = false;

[abarth-chromium, 2014/03/05 00:27:35]

Why do we only scan the first chunk?  What if |length| is 1?  It seems better to
scan until we've reached some state in the preload scanner..

+        CSSPreloadScanner m_preloadScanner;
+        PreloadRequestStream pendingPreloads;
+        m_preloadScanner.scan(data, SegmentedString(data), pendingPreloads);
+
+        HTMLResourcePreloader m_preloader(&document());
+        m_preloader.takeAndPreload(pendingPreloads);
+    }
+}
+
 bool LinkStyle::sheetLoaded()
 {
     if (!styleSheetIsLoading()) {