scheduler: Detect load RAIL mode

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/LocalFrame.h"
 #include "core/loader/DocumentLoader.h"
 #include "platform/tracing/TraceEvent.h"
+#include "public/platform/WebFrameScheduler.h"
 
 namespace blink {
 
 static const char kSupplementName[] = "PaintTiming";
 
 PaintTiming& PaintTiming::from(Document& document) {
   PaintTiming* timing = static_cast<PaintTiming*>(
       Supplement<Document>::from(document, kSupplementName));
   if (!timing) {
     timing = new PaintTiming(document);
@@ skipping 38 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() {
+  // The first meaningful paint candidate can be reported very early, even
+  // before the first contentful paint. To cut down on false positives, we only
+  // report the first meaningful paint candidate after the first contentful
+  // paint.
+  if (!m_firstContentfulPaint)

[Kunihiko Sakamoto, 2016/10/13 08:01:34]

Within a single paint phase, this runs after
PaintTiming::setFirstContentfulPaint(). So this won't skip FCP if it is a FMP
candidate. Is that OK?

[Sami, 2016/10/13 08:23:59]

Good point. Perhaps the thing to do is to ignore the first FMP candidate after
FCP with the theory that it is usually the FCP itself.

[Kunihiko Sakamoto, 2016/10/13 08:38:46]

Yeah, I think patch set 9 would work.

+    return;
+  if (m_document->frame() && m_document->frame()->view() &&
+      !m_document->frame()->view()->parent()) {
+    m_document->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",
       TraceEvent::toTraceTimestamp(m_firstMeaningfulPaint), "frame", frame());
   notifyPaintTimingChanged();
 }
 
 void PaintTiming::notifyPaint(bool isFirstPaint,
@@ skipping 38 matching lines @@
 void PaintTiming::setFirstContentfulPaint(double stamp) {
   if (m_firstContentfulPaint != 0.0)
     return;
   setFirstPaint(stamp);
   m_firstContentfulPaint = stamp;
   TRACE_EVENT_INSTANT1("blink.user_timing,rail", "firstContentfulPaint",
                        TRACE_EVENT_SCOPE_PROCESS, "frame", frame());
 }
 
 }  // namespace blink