Ensure the scheduler always changes from UseCase LOADING to NONE.

third_party/WebKit/Source/core/paint/FirstMeaningfulPaintDetector.cpp

Index: third_party/WebKit/Source/core/paint/FirstMeaningfulPaintDetector.cpp
diff --git a/third_party/WebKit/Source/core/paint/FirstMeaningfulPaintDetector.cpp b/third_party/WebKit/Source/core/paint/FirstMeaningfulPaintDetector.cpp
index 9fca4136977ee48f1cbc383fcf7596b21f0748de..4abe2da6e76965590e20c4ccb611f559bb763b1d 100644
--- a/third_party/WebKit/Source/core/paint/FirstMeaningfulPaintDetector.cpp
+++ b/third_party/WebKit/Source/core/paint/FirstMeaningfulPaintDetector.cpp
@@ -104,7 +104,8 @@ void FirstMeaningfulPaintDetector::notifyPaint() {
     m_seenFirstMeaningfulPaintCandidate = true;
     return;
   }
-  m_paintTiming->markFirstMeaningfulPaintCandidate();
+  m_paintTiming->markFirstMeaningfulPaintCandidate(
+      m_provisionalFirstMeaningfulPaint);
 }
 
 void FirstMeaningfulPaintDetector::checkNetworkStable() {
@@ -123,6 +124,11 @@ void FirstMeaningfulPaintDetector::networkStableTimerFired(TimerBase*) {
     return;
 
   if (m_provisionalFirstMeaningfulPaint) {
+    // If there's only been one contentful paint, then there won't have been
+    // a meaningful paint signalled to the Scheduler, so mark one now.
+    // This is a no-op if a FMPC has already been marked.
+    m_paintTiming->markFirstMeaningfulPaintCandidate(
+        m_provisionalFirstMeaningfulPaint);
     // Enforce FirstContentfulPaint <= FirstMeaningfulPaint.
     double timestamp = std::max(m_provisionalFirstMeaningfulPaint,
                                 m_paintTiming->firstContentfulPaint());