Prefetch @import files from CSS files.

Source/core/html/HTMLLinkElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Rob Buis (rwlbuis@gmail.com)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 28 matching lines @@
 #include "core/events/EventSender.h"
 #include "core/fetch/CSSStyleSheetResource.h"
 #include "core/fetch/FetchRequest.h"
 #include "core/fetch/ResourceFetcher.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/SubresourceIntegrity.h"
 #include "core/frame/csp/ContentSecurityPolicy.h"
 #include "core/html/LinkManifest.h"
 #include "core/html/imports/LinkImport.h"
+#include "core/html/parser/CompactHTMLToken.h"
 #include "core/loader/FrameLoader.h"
 #include "core/loader/FrameLoaderClient.h"
 #include "core/rendering/style/StyleInheritedData.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "wtf/StdLibExtras.h"
 
 namespace blink {
 
 using namespace HTMLNames;
 
@@ skipping 414 matching lines @@
     HTMLElement::attributeWillChange(name, oldValue, newValue);
 }
 
 PassOwnPtrWillBeRawPtr<LinkStyle> LinkStyle::create(HTMLLinkElement* owner)
 {
     return adoptPtrWillBeNoop(new LinkStyle(owner));
 }
 
 LinkStyle::LinkStyle(HTMLLinkElement* owner)
     : LinkResource(owner)
+    , m_token(adoptPtr(new HTMLToken))
+    , m_tokenizer(HTMLTokenizer::create(m_options))
+    , m_preloadScanner(adoptPtr(new CSSPreloadScanner))
+    , m_preloadLength(0)
     , m_disabledState(Unset)
     , m_pendingSheetType(None)
     , m_loading(false)
     , m_firedLoad(false)
     , m_loadedSheet(false)
 {
+    // The tokenizer uses RAWTEXTState to identify the origin of a request.
+    // This state is also used while handling CSS prefetch in the html parser.
+    m_tokenizer->setState(HTMLTokenizer::RAWTEXTState);
 }
 
 LinkStyle::~LinkStyle()
 {
 #if !ENABLE(OILPAN)
     if (m_sheet)
         m_sheet->clearOwnerNode();
 #endif
 }
 
@@ skipping 48 matching lines @@
     styleSheet->parseAuthorStyleSheet(cachedStyleSheet, m_owner->document().securityOrigin());
 
     m_loading = false;
     styleSheet->notifyLoadedSheet(cachedStyleSheet);
     styleSheet->checkLoaded();
 
     if (styleSheet->isCacheable())
         const_cast<CSSStyleSheetResource*>(cachedStyleSheet)->saveParsedStyleSheet(styleSheet);
 }
 
+void LinkStyle::dataReceived(const CSSStyleSheetResource* cachedStyleSheet)
+{
+    if (!m_preloadScanner)

[Yoav Weiss, 2015/01/05 13:18:44]

Maybe a comment saying that the absence of m_preloadScanner means that we passed
the "@import" phase of that resource?

[jonnyr, 2015/01/06 00:13:06]

Done.

+        return;
+
+    PreloadRequestStream pendingPreloads;
+    String sheetText = cachedStyleSheet->sheetText();
+    if (sheetText.length() == m_preloadLength)
+        return;
+
+    m_input.append(sheetText.substring(m_preloadLength));
+
+    while (true) {
+

[Yoav Weiss, 2015/01/05 13:18:44]

Why not merge the if condition into the while loop?

Something like:
    while (m_tokenizer->nextToken(m_input.current(), *m_token)) {
        Compact.....


    } 

[jonnyr, 2015/01/06 00:13:06]

Done.

+        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);
+        }
+        m_token->clear();
+    }
+
+    m_preloadLength = sheetText.length();
+
+    OwnPtr<HTMLResourcePreloader> preloader = HTMLResourcePreloader::create(document());
+    preloader->takeAndPreload(pendingPreloads);
+    if (m_preloadScanner->isDoneParsingImports()) {
+        // Note: Although dataRecieved will be called for each packet of data
+        // returned from the network, @import statements are always at the top
+        // of the CSS file. As soon as we reach a part of the CSS file which
+        // is not an @import we can delete our preloader and ignore the rest of
+        // file. If we ever make CSS preloading more complicated (to look for
+        // URLs other than @imports) we will need to re-think this logic.
+        m_preloadScanner.clear();
+        m_tokenizer.clear();
+        m_token.clear();
+    }
+}
+
 bool LinkStyle::sheetLoaded()
 {
     if (!styleSheetIsLoading()) {
         removePendingSheet();
         return true;
     }
     return false;
 }
 
 void LinkStyle::notifyLoadedSheetAndAllCriticalSubresources(bool errorOccurred)
@@ skipping 184 matching lines @@
         removePendingSheet();
 }
 
 void LinkStyle::trace(Visitor* visitor)
 {
     visitor->trace(m_sheet);
     LinkResource::trace(visitor);
 }
 
 } // namespace blink