[LazyParseCSS] Add metrics for total # of rules at 0% and 100% usage

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

 // 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.
 
 #include "core/css/parser/CSSLazyParsingState.h"
 #include "core/css/parser/CSSLazyPropertyParserImpl.h"
 #include "core/css/parser/CSSParserTokenRange.h"
 #include "core/dom/Document.h"
 #include "core/frame/UseCounter.h"
 #include "platform/Histogram.h"
 
 namespace blink {
 
 CSSLazyParsingState::CSSLazyParsingState(const CSSParserContext* context,
                                          Vector<String> escapedStrings,
                                          const String& sheetText,
                                          StyleSheetContents* contents)
     : m_context(context),
       m_escapedStrings(std::move(escapedStrings)),
       m_sheetText(sheetText),
       m_owningContents(contents),
       m_parsedStyleRules(0),
       m_totalStyleRules(0),
       m_styleRulesNeededForNextMilestone(0),
       m_usage(UsageGe0),
-      m_shouldUseCount(m_context->isUseCounterRecordingEnabled()) {
+      m_shouldUseCount(m_context->isUseCounterRecordingEnabled()) {}
+
+void CSSLazyParsingState::finishInitialParsing() {
   recordUsageMetrics();
 }
 
 CSSLazyPropertyParserImpl* CSSLazyParsingState::createLazyParser(
     const CSSParserTokenRange& block) {
   ++m_totalStyleRules;
   return new CSSLazyPropertyParserImpl(std::move(block), this);
 }
 
 const CSSParserContext* CSSLazyParsingState::context() {
@@ skipping 47 matching lines @@
       if (current->relation() != CSSSelector::SubSelector)
         break;
     }
   }
   return true;
 }
 
 void CSSLazyParsingState::recordUsageMetrics() {
   DEFINE_STATIC_LOCAL(EnumerationHistogram, usageHistogram,
                       ("Style.LazyUsage.Percent", UsageLastValue));
+  DEFINE_STATIC_LOCAL(CustomCountHistogram, totalRulesHistogram,
+                      ("Style.TotalLazyRules", 0, 100000, 50));
+  DEFINE_STATIC_LOCAL(CustomCountHistogram, totalRulesFullUsageHistogram,
+                      ("Style.TotalLazyRules.FullUsage", 0, 100000, 50));
   switch (m_usage) {
     case UsageGe0:
+      totalRulesHistogram.count(m_totalStyleRules);
       m_styleRulesNeededForNextMilestone = m_totalStyleRules * .1;
       break;
     case UsageGt10:
       m_styleRulesNeededForNextMilestone = m_totalStyleRules * .25;
       break;
     case UsageGt25:
       m_styleRulesNeededForNextMilestone = m_totalStyleRules * .5;
       break;
     case UsageGt50:
       m_styleRulesNeededForNextMilestone = m_totalStyleRules * .75;
       break;
     case UsageGt75:
       m_styleRulesNeededForNextMilestone = m_totalStyleRules * .9;
       break;
     case UsageGt90:
       m_styleRulesNeededForNextMilestone = m_totalStyleRules - 1;
       break;
     case UsageAll:
+      totalRulesFullUsageHistogram.count(m_totalStyleRules);
       m_styleRulesNeededForNextMilestone = m_totalStyleRules;
       break;
   }
 
   usageHistogram.count(m_usage);
 }
 
 DEFINE_TRACE(CSSLazyParsingState) {
   visitor->trace(m_owningContents);
   visitor->trace(m_document);
   visitor->trace(m_context);
 }
 
 }  // namespace blink