Lazy Parse CSS

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

Index: third_party/WebKit/Source/core/css/StyleSheetContents.cpp
diff --git a/third_party/WebKit/Source/core/css/StyleSheetContents.cpp b/third_party/WebKit/Source/core/css/StyleSheetContents.cpp
index 6d642af4888d5b79bc5cac7c863150036f994e5a..8efbdbb15a1dffc0b069af4b59212a5d10146a10 100644
--- a/third_party/WebKit/Source/core/css/StyleSheetContents.cpp
+++ b/third_party/WebKit/Source/core/css/StyleSheetContents.cpp
@@ -90,6 +90,8 @@ StyleSheetContents::StyleSheetContents(const StyleSheetContents& o)
   // 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();
 }
@@ -349,7 +351,8 @@ void StyleSheetContents::parseAuthorStyleSheet(
   }
 
   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) {
@@ -476,7 +479,7 @@ static bool childRulesHaveFailedOrCanceledSubresources(
     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: