[LazyParseCSS] Add histogram for rule usage %

third_party/WebKit/Source/core/css/parser/CSSParserImpl.cpp

 // Copyright 2014 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.
 
 #include "core/css/parser/CSSParserImpl.h"
 
 #include "core/css/CSSCustomIdentValue.h"
 #include "core/css/CSSCustomPropertyDeclaration.h"
 #include "core/css/CSSKeyframesRule.h"
 #include "core/css/CSSStyleSheet.h"
@@ skipping 783 matching lines @@
       CSSSelectorParser::parseSelector(prelude, m_context, m_styleSheet);
   if (!selectorList.isValid())
     return nullptr;  // Parse error, invalid selector list
 
   // TODO(csharrison): How should we lazily parse css that needs the observer?
   if (m_observerWrapper) {
     observeSelectors(*m_observerWrapper, prelude);
   } else if (m_lazyState &&
              m_lazyState->shouldLazilyParseProperties(selectorList, block)) {
     DCHECK(m_styleSheet);
-    return StyleRule::createLazy(
-        std::move(selectorList),
-        new CSSLazyPropertyParserImpl(block, m_lazyState));
+    return StyleRule::createLazy(std::move(selectorList),
+                                 m_lazyState->createLazyParser(block));
   }
   consumeDeclarationList(block, StyleRule::Style);
 
   return StyleRule::create(
       std::move(selectorList),
       createStylePropertySet(m_parsedProperties, m_context.mode()));
 }
 
 void CSSParserImpl::consumeDeclarationList(CSSParserTokenRange range,
                                            StyleRule::RuleType ruleType) {
@@ skipping 148 matching lines @@
     else
       return nullptr;  // Parser error, invalid value in keyframe selector
     if (range.atEnd())
       return result;
     if (range.consume().type() != CommaToken)
       return nullptr;  // Parser error
   }
 }
 
 }  // namespace blink