[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..1c872baa2301eb28e15eb43500c27b80180cda8c 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::finishStrictParsing() {

[rune, 2017/02/10 10:33:52]

I was confused by the name. When I see "strict", I think "strict" as opposed to
"quirks" mode. Would something like "initial" or "minimal" be better?

[Charlie Harrison, 2017/02/10 12:49:42]

Done. Changed to "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;
   }