Bug 1506976 - Make FirstContentfulPaint timing measure until the composite end of the paint. r=bas

Differential Revision: https://phabricator.services.mozilla.com/D18880

--HG--
extra : moz-landing-system : lando

dom/base/nsDOMNavigationTiming.cpp

@@ -414,7 +414,8 @@ void nsDOMNavigationTiming::NotifyNonBlankPaintForRootContentDocument() {
   }
 }
 
-void nsDOMNavigationTiming::NotifyContentfulPaintForRootContentDocument() {
+void nsDOMNavigationTiming::NotifyContentfulPaintForRootContentDocument(
+    const mozilla::TimeStamp& aCompositeEndTime) {
   MOZ_ASSERT(NS_IsMainThread());
   MOZ_ASSERT(!mNavigationStart.IsNull());
 
@@ -422,7 +423,7 @@ void nsDOMNavigationTiming::NotifyContentfulPaintForRootContentDocument() {
     return;
   }
 
-  mContentfulPaint = TimeStamp::Now();
+  mContentfulPaint = aCompositeEndTime;
 
 #ifdef MOZ_GECKO_PROFILER
   if (profiler_is_active() || PAGELOAD_LOG_ENABLED()) {

dom/base/nsDOMNavigationTiming.h

@@ -142,7 +142,8 @@ class nsDOMNavigationTiming final : public mozilla::RelativeTimeline {
 
   void NotifyLongTask(mozilla::TimeStamp aWhen);
   void NotifyNonBlankPaintForRootContentDocument();
-  void NotifyContentfulPaintForRootContentDocument();
+  void NotifyContentfulPaintForRootContentDocument(
+      const mozilla::TimeStamp& aCompositeEndTime);
   void NotifyDOMContentFlushedForRootContentDocument();
   void NotifyDocShellStateChanged(DocShellState aDocShellState);
 

layout/base/nsPresContext.cpp

@@ -232,7 +232,8 @@ nsPresContext::nsPresContext(dom::Document* aDocument, nsPresContextType aType)
       mQuirkSheetAdded(false),
       mNeedsPrefUpdate(false),
       mHadNonBlankPaint(false),
-      mHadContentfulPaint(false)
+      mHadContentfulPaint(false),
+      mHadContentfulPaintComposite(false)
 #ifdef DEBUG
       ,
       mInitialized(false)
@@ -2265,6 +2266,16 @@ void nsPresContext::NotifyRevokingDidPaint(TransactionId aTransactionId) {
 
 void nsPresContext::NotifyDidPaintForSubtree(
     TransactionId aTransactionId, const mozilla::TimeStamp& aTimeStamp) {
+  if (mFirstContentfulPaintTransactionId && !mHadContentfulPaintComposite) {
+    if (aTransactionId >= *mFirstContentfulPaintTransactionId) {
+      mHadContentfulPaintComposite = true;
+      RefPtr<nsDOMNavigationTiming> timing = mDocument->GetNavigationTiming();
+      if (timing) {
+        timing->NotifyContentfulPaintForRootContentDocument(aTimeStamp);
+      }
+    }
+  }
+
   if (IsRoot() && mTransactions.IsEmpty()) {
     return;
   }
@@ -2545,12 +2556,10 @@ void nsPresContext::NotifyContentfulPaint() {
   if (!mHadContentfulPaint) {
     mHadContentfulPaint = true;
     if (IsRootContentDocument()) {
-      RefPtr<nsDOMNavigationTiming> timing = mDocument->GetNavigationTiming();
-      if (timing) {
-        timing->NotifyContentfulPaintForRootContentDocument();
+      if (nsRootPresContext* rootPresContext = GetRootPresContext()) {
+        mFirstContentfulPaintTransactionId =
+            Some(rootPresContext->mRefreshDriver->LastTransactionId().Next());
       }
-
-      mFirstContentfulPaintTime = TimeStamp::Now();
     }
   }
 }

layout/base/nsPresContext.h

@@ -1265,14 +1265,16 @@ class nsPresContext : public nsISupports,
 
   mozilla::TimeStamp mReflowStartTime;
 
+  mozilla::Maybe<TransactionId> mFirstContentfulPaintTransactionId;
+
   // Time of various first interaction types, used to report time from
   // first paint of the top level content pres shell to first interaction.
   mozilla::TimeStamp mFirstNonBlankPaintTime;
-  mozilla::TimeStamp mFirstContentfulPaintTime;
   mozilla::TimeStamp mFirstClickTime;
   mozilla::TimeStamp mFirstKeyTime;
   mozilla::TimeStamp mFirstMouseMoveTime;
   mozilla::TimeStamp mFirstScrollTime;
+
   bool mInteractionTimeEnabled;
 
   // last time we did a full style flush
@@ -1346,6 +1348,8 @@ class nsPresContext : public nsISupports,
   unsigned mHadNonBlankPaint : 1;
   // Has NotifyContentfulPaint been called on this PresContext?
   unsigned mHadContentfulPaint : 1;
+  // Has NotifyDidPaintForSubtree been called for a contentful paint?
+  unsigned mHadContentfulPaintComposite : 1;
 
 #ifdef DEBUG
   unsigned mInitialized : 1;