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

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

Index: third_party/WebKit/Source/core/css/parser/CSSLazyParsingState.cpp
diff --git a/third_party/WebKit/Source/core/css/parser/CSSLazyParsingState.cpp b/third_party/WebKit/Source/core/css/parser/CSSLazyParsingState.cpp
index c5ed81cc30a8bbd6fa11196056f1df49ca57964b..b61e716c9cb99fdd7622b7a4ba18b05d237daa24 100644
--- a/third_party/WebKit/Source/core/css/parser/CSSLazyParsingState.cpp
+++ b/third_party/WebKit/Source/core/css/parser/CSSLazyParsingState.cpp
@@ -23,7 +23,9 @@ CSSLazyParsingState::CSSLazyParsingState(const CSSParserContext* context,
       m_totalStyleRules(0),
       m_styleRulesNeededForNextMilestone(0),
       m_usage(UsageGe0),
-      m_shouldUseCount(m_context->isUseCounterRecordingEnabled()) {
+      m_shouldUseCount(m_context->isUseCounterRecordingEnabled()) {}
+
+void CSSLazyParsingState::finishInitialParsing() {
   recordUsageMetrics();
 }
 
@@ -91,8 +93,13 @@ bool CSSLazyParsingState::shouldLazilyParseProperties(
 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:
@@ -111,6 +118,7 @@ void CSSLazyParsingState::recordUsageMetrics() {
       m_styleRulesNeededForNextMilestone = m_totalStyleRules - 1;
       break;
     case UsageAll:
+      totalRulesFullUsageHistogram.count(m_totalStyleRules);
       m_styleRulesNeededForNextMilestone = m_totalStyleRules;
       break;
   }