Ensure the scheduler always changes from UseCase LOADING to NONE.

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

 // Copyright 2015 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/paint/PaintTiming.h"
 
 #include "core/dom/Document.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalDOMWindow.h"
 #include "core/frame/LocalFrame.h"
@@ skipping 65 matching lines @@
   if (m_firstImagePaint != 0.0)
     return;
   m_firstImagePaint = monotonicallyIncreasingTime();
   setFirstContentfulPaint(m_firstImagePaint);
   TRACE_EVENT_MARK_WITH_TIMESTAMP1(
       "blink.user_timing,rail", "firstImagePaint",
       TraceEvent::toTraceTimestamp(m_firstImagePaint), "frame", frame());
   notifyPaintTimingChanged();
 }
 
-void PaintTiming::markFirstMeaningfulPaintCandidate() {
+void PaintTiming::setFirstMeaningfulPaintCandidate(double timestamp) {
   if (m_firstMeaningfulPaintCandidate)
     return;
-  m_firstMeaningfulPaintCandidate = monotonicallyIncreasingTime();
+  m_firstMeaningfulPaintCandidate = timestamp;
   if (frame() && frame()->view() && !frame()->view()->parent()) {
     frame()->frameScheduler()->onFirstMeaningfulPaint();
   }
 }
 
 void PaintTiming::setFirstMeaningfulPaint(double stamp) {
   DCHECK_EQ(m_firstMeaningfulPaint, 0.0);
   m_firstMeaningfulPaint = stamp;
   TRACE_EVENT_MARK_WITH_TIMESTAMP1(
       "blink.user_timing", "firstMeaningfulPaint",
@@ skipping 49 matching lines @@
   setFirstPaint(stamp);
   m_firstContentfulPaint = stamp;
   Performance* performance = getPerformanceInstance(frame());
   if (performance)
     performance->addFirstContentfulPaintTiming(m_firstContentfulPaint);
   TRACE_EVENT_INSTANT1("blink.user_timing,rail", "firstContentfulPaint",
                        TRACE_EVENT_SCOPE_PROCESS, "frame", frame());
 }
 
 }  // namespace blink