Lazy Parse CSS

third_party/WebKit/Source/core/css/StyleSheetContents.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2006, 2007, 2012 Apple 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 72 matching lines @@
       m_didLoadErrorOccur(false),
       m_isMutable(false),
       m_hasFontFaceRule(o.m_hasFontFaceRule),
       m_hasMediaQueries(o.m_hasMediaQueries),
       m_hasSingleOwnerDocument(true),
       m_isUsedFromTextCache(false),
       m_parserContext(o.m_parserContext) {
   // FIXME: Copy import rules.
   ASSERT(o.m_importRules.isEmpty());
 
+  // LazyParseCSS: Copying child rules is a strict point for lazy parsing, so
+  // there is no need to copy lazy parsing state here.
   for (unsigned i = 0; i < m_childRules.size(); ++i)
     m_childRules[i] = o.m_childRules[i]->copy();
 }
 
 StyleSheetContents::~StyleSheetContents() {}
 
 void StyleSheetContents::setHasSyntacticallyValidCSSHeader(bool isValidCss) {
   m_hasSyntacticallyValidCSSHeader = isValidCss;
 }
 
@@ skipping 239 matching lines @@
   String sheetText = cachedStyleSheet->sheetText(mimeTypeCheck);
 
   const ResourceResponse& response = cachedStyleSheet->response();
   m_sourceMapURL = response.httpHeaderField(HTTPNames::SourceMap);
   if (m_sourceMapURL.isEmpty()) {
     // Try to get deprecated header.
     m_sourceMapURL = response.httpHeaderField(HTTPNames::X_SourceMap);
   }
 
   CSSParserContext context(parserContext(), UseCounter::getFrom(this));
-  CSSParser::parseSheet(context, this, sheetText);
+  CSSParser::parseSheet(context, this, sheetText,
+                        RuntimeEnabledFeatures::lazyParseCSSEnabled());

[esprehn, 2016/10/24 21:20:20]

Can we check this flag from inside parseSheet instead of passing the boolean?

[Charlie Harrison, 2016/10/25 15:56:55]

It's a bit tricky and involves tradeoffs. Passing the flag entails that we will
hold reference to the decoded bytes of the sheet. Right now, to not regress
memory, we only want to do this for sheets that are backed by a css resource,
which hold on to the decoded bytes already.

I am interested in possibly turning the optimization on for the other types of
sheets (inline, UA, inserted, etc). I am just nervous/cautious about the memory.

 }
 
 void StyleSheetContents::parseString(const String& sheetText) {
   parseStringAtPosition(sheetText, TextPosition::minimumPosition());
 }
 
 void StyleSheetContents::parseStringAtPosition(
     const String& sheetText,
     const TextPosition& startPosition) {
   CSSParserContext context(parserContext(), UseCounter::getFrom(this));
@@ skipping 106 matching lines @@
   StyleSheetContents* root = rootStyleSheet();
   return root->clientSingleOwnerDocument();
 }
 
 static bool childRulesHaveFailedOrCanceledSubresources(
     const HeapVector<Member<StyleRuleBase>>& rules) {
   for (unsigned i = 0; i < rules.size(); ++i) {
     const StyleRuleBase* rule = rules[i].get();
     switch (rule->type()) {
       case StyleRuleBase::Style:
-        if (toStyleRule(rule)->properties().hasFailedOrCanceledSubresources())
+        if (toStyleRule(rule)->propertiesHaveFailedOrCanceledSubresources())
           return true;
         break;
       case StyleRuleBase::FontFace:
         if (toStyleRuleFontFace(rule)
                 ->properties()
                 .hasFailedOrCanceledSubresources())
           return true;
         break;
       case StyleRuleBase::Media:
         if (childRulesHaveFailedOrCanceledSubresources(
@@ skipping 174 matching lines @@
   visitor->trace(m_importRules);
   visitor->trace(m_namespaceRules);
   visitor->trace(m_childRules);
   visitor->trace(m_loadingClients);
   visitor->trace(m_completedClients);
   visitor->trace(m_ruleSet);
   visitor->trace(m_referencedFromResource);
 }
 
 }  // namespace blink