[LazyParseCSS] Ensure UseCounting has parity with strict parsing

third_party/WebKit/Source/core/css/parser/CSSLazyParsingState.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CSSLazyParsingState_h
 #define CSSLazyParsingState_h
 
 #include "core/css/CSSSelectorList.h"
 #include "core/css/StyleSheetContents.h"
 #include "core/css/parser/CSSParserMode.h"
@@ skipping 19 matching lines @@
   // Helper method used to bump m_totalStyleRules.
   CSSLazyPropertyParserImpl* createLazyParser(const CSSParserTokenRange& block);
 
   const CSSParserContext& context();
 
   void countRuleParsed();
 
   bool shouldLazilyParseProperties(const CSSSelectorList&,
                                    const CSSParserTokenRange& block) const;
 
-  DEFINE_INLINE_TRACE() { visitor->trace(m_owningContents); }
+  DECLARE_TRACE();
 
   // Exposed for tests. This enum is used to back a histogram, so new values
   // must be appended to the end, before UsageLastValue.
   enum CSSRuleUsage {
     UsageGe0 = 0,
     UsageGt10 = 1,
     UsageGt25 = 2,
     UsageGt50 = 3,
     UsageGt75 = 4,
     UsageGt90 = 5,
     UsageAll = 6,
 
     // This value must be last.
     UsageLastValue = 7
   };
 
  private:
   void recordUsageMetrics();
 
   CSSParserContext m_context;
   Vector<String> m_escapedStrings;
   // Also referenced on the css resource.
   String m_sheetText;
 
   // Weak to ensure lazy state will never cause the contents to live longer than
   // it should (we DCHECK this fact).
   WeakMember<StyleSheetContents> m_owningContents;
 
+  // Cache the document as a proxy for caching the UseCounter. Grabbing the
+  // UseCounter per every property parse is a bit more expensive.
+  WeakMember<Document> m_document;
+
   // Used for calculating the % of rules that ended up being parsed.
   int m_parsedStyleRules;
   int m_totalStyleRules;
 
   int m_styleRulesNeededForNextMilestone;
 
   int m_usage;
+
+  // Whether or not use counting is enabled for parsing. This will usually be
+  // true, except for when stylesheets with @imports are removed from the page.
+  // See StyleRuleImport::setCSSStyleSheet.
+  const bool m_shouldUseCount;
 };
 
 }  // namespace blink
 
 #endif  // CSSLazyParsingState_h