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 3ee6600b7302235de6b0ff3d4cefcf801407c2f1..c969af88ebf487e64fae3156fd78d13b739d075a 100644
--- a/Source/core/html/HTMLLinkElement.cpp
+++ b/Source/core/html/HTMLLinkElement.cpp
@@ -436,6 +436,8 @@ PassOwnPtrWillBeRawPtr<LinkStyle> LinkStyle::create(HTMLLinkElement* owner)
 
 LinkStyle::LinkStyle(HTMLLinkElement* owner)
     : LinkResource(owner)
+    , m_preloadScanner(adoptPtr(new CSSPreloadScanner))
+    , m_input(adoptPtr(new SegmentedString))

[eseidel, 2014/05/20 07:10:37]

You might want to name this m_preloaderInput?  Since it's specific to the
preloader?

     , m_disabledState(Unset)
     , m_pendingSheetType(None)
     , m_loading(false)
@@ -502,6 +504,21 @@ 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_preloadScanner.get()) {

[eseidel, 2014/05/20 06:27:04]

Normally these are written as early returns.

if (!m_preloadScannner)
   return;

+        PreloadRequestStream pendingPreloads;
+        m_input->append(SegmentedString(data));
+        m_preloadScanner->scan(data, *m_input, pendingPreloads);
+        HTMLResourcePreloader m_preloader(&document());
+        m_preloader.takeAndPreload(pendingPreloads);
+        if (m_preloadScanner->isDoneParsing()) {

[eseidel, 2014/05/20 06:27:04]

I'm not familiar with this method.  How does the preload scanner know when the
document is done?

+            m_preloadScanner.clear();
+            m_input.clear();
+        }
+    }
+}
+
 bool LinkStyle::sheetLoaded()
 {
     if (!styleSheetIsLoading()) {