scheduler: Detect load RAIL mode

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

 // 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.
 
 #ifndef PaintTiming_h
 #define PaintTiming_h
 
 #include "core/dom/Document.h"
 #include "core/paint/FirstMeaningfulPaintDetector.h"
 #include "platform/Supplementable.h"
@@ skipping 25 matching lines @@
 
   // markFirstTextPaint, markFirstImagePaint, and markFirstContentfulPaint
   // will also record first paint if first paint hasn't been recorded yet.
   void markFirstContentfulPaint();
 
   // markFirstTextPaint and markFirstImagePaint will also record first
   // contentful paint if first contentful paint hasn't been recorded yet.
   void markFirstTextPaint();
   void markFirstImagePaint();
 
+  void markFirstMeaningfulPaintCandidate();
   void setFirstMeaningfulPaint(double stamp);
   void notifyPaint(bool isFirstPaint, bool textPainted, bool imagePainted);
 
   // The getters below return monotonically-increasing seconds, or zero if the
   // given paint event has not yet occurred. See the comments for
   // monotonicallyIncreasingTime in wtf/CurrentTime.h for additional details.
 
   // firstPaint returns the first time that anything was painted for the
   // current document.
   double firstPaint() const { return m_firstPaint; }
@@ skipping 36 matching lines @@
   // setFirstContentfulPaint will also set first paint time if first paint
   // time has not yet been recorded.
   void setFirstContentfulPaint(double stamp);
 
   double m_firstPaint = 0.0;
   double m_firstTextPaint = 0.0;
   double m_firstImagePaint = 0.0;
   double m_firstContentfulPaint = 0.0;
   double m_firstMeaningfulPaint = 0.0;
 
+  bool m_seenFirstMeaningfulPaintCandidate = false;

[kouhei (in TOK), 2016/11/30 01:30:20]

We prefer this flag/logic to be inside FirstMeaningfulPaintDetector

[kouhei (in TOK), 2016/11/30 01:36:52]

Chatted offline w/ ksakamoto.

I think we have two options (we are fine with either one):
- FMP<FCP on very rare cases (like drawing pictures w/ CSS boxes
http://purecss3.net/doraemon/doraemon_css3.html o_O) so we can safely ignore
them.
- If you would like to keep this logic, please move this flag/logic to
FirstMeaningfulPaintDetector

[Sami, 2016/11/30 18:07:09]

Great example :)
I've now moved this to FirstMeaningfulPaintDetector and modified it so that we
don't mind if FMP<FCP, but we still ignore the first FMP_c so that we don't
declare success too early. Does that sound like a good compromise?

+
   Member<Document> m_document;
   Member<FirstMeaningfulPaintDetector> m_fmpDetector;
 };
 
 }  // namespace blink
 
 #endif