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 be920489f280bb79685f86cff7c37bad9b17caeb..7cde684da5eda39ce0a57fcf493aee40b2f29532 100644
--- a/Source/core/fetch/CSSStyleSheetResource.cpp
+++ b/Source/core/fetch/CSSStyleSheetResource.cpp
@@ -30,6 +30,7 @@
 #include "core/css/StyleSheetContents.h"
 #include "core/fetch/ResourceClientWalker.h"
 #include "core/fetch/StyleSheetResourceClient.h"
+#include "core/html/parser/CompactHTMLToken.h"
 #include "core/html/parser/TextResourceDecoder.h"
 #include "platform/SharedBuffer.h"
 #include "platform/network/HTTPParsers.h"
@@ -38,15 +39,22 @@
 
 namespace WebCore {
 
-CSSStyleSheetResource::CSSStyleSheetResource(const ResourceRequest& resourceRequest, const String& charset)
+CSSStyleSheetResource::CSSStyleSheetResource(const ResourceRequest& resourceRequest, const String& charset, Document* document)
     : StyleSheetResource(resourceRequest, CSSStyleSheet)
     , m_decoder(TextResourceDecoder::create("text/css", charset))
+    , m_tokenizer(HTMLTokenizer::create(m_options))
+    , m_preloadScanner(adoptPtr(new CSSPreloadScanner))
+    , m_input(adoptPtr(new BackgroundHTMLInputStream))
+    , m_token(adoptPtr(new HTMLToken))
+    , m_preloader(adoptPtr(new HTMLResourcePreloader(document)))
+    , m_prescan(true)
 {
     DEFINE_STATIC_LOCAL(const AtomicString, acceptCSS, ("text/css,*/*;q=0.1", AtomicString::ConstructFromLiteral));
 
     // Prefer text/css but accept any type (dell.com serves a stylesheet
     // as text/html; see <http://bugs.webkit.org/show_bug.cgi?id=11451>).
     setAccept(acceptCSS);
+    m_tokenizer->setState(HTMLTokenizer::RAWTEXTState);
 }
 
 CSSStyleSheetResource::~CSSStyleSheetResource()
@@ -108,6 +116,32 @@ void CSSStyleSheetResource::checkNotify()
     m_decodedSheetText = String();
 }
 
+void CSSStyleSheetResource::appendData(const char* data, int length)
+{
+    Resource::appendData(data, length);
+    if (m_prescan) {
+        // FIXME: Allow scanning entire CSS file for background images and prefetch according to applied rules.
+        m_prescan = false;
+        prescan(data);
+    }
+}
+
+void CSSStyleSheetResource::prescan(const char* data)
+{
+    PreloadRequestStream pendingPreloads;
+    m_input->append(data);
+
+    while (true) {
+        if (!m_tokenizer->nextToken(m_input->current(), *m_token))
+            break; // We've reached the end of our current input.
+
+        CompactHTMLToken token(m_token.get(), TextPosition(m_input->current().currentLine(), m_input->current().currentColumn()));
+        m_preloadScanner->scan(token.data(), m_input->current(), pendingPreloads);

[shatch, 2014/02/14 16:20:17]

What's the advantage to running this through the tokenizer before sending it to
the preload scanner? Otherwise, seems like it would be cleaner to just send the
data directly.

+        m_token->clear();
+    }
+    m_preloader->takeAndPreload(pendingPreloads);
+}
+
 bool CSSStyleSheetResource::canUseSheet(bool enforceMIMEType, bool* hasValidMIMEType) const
 {
     if (errorOccurred())