scheduler: Detect load RAIL mode

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

Index: third_party/WebKit/Source/core/paint/PaintTiming.h
diff --git a/third_party/WebKit/Source/core/paint/PaintTiming.h b/third_party/WebKit/Source/core/paint/PaintTiming.h
index 488a2a3b68c5134ae9d75721e8d26f1fdc33b356..dffe87eb4354582e7d3c04a894d34cd1d056cf3c 100644
--- a/third_party/WebKit/Source/core/paint/PaintTiming.h
+++ b/third_party/WebKit/Source/core/paint/PaintTiming.h
@@ -43,6 +43,7 @@ class CORE_EXPORT PaintTiming final
   void markFirstTextPaint();
   void markFirstImagePaint();
 
+  void markFirstMeaningfulPaintCandidate();
   void setFirstMeaningfulPaint(double stamp);
   void notifyPaint(bool isFirstPaint, bool textPainted, bool imagePainted);
 
@@ -99,6 +100,8 @@ class CORE_EXPORT PaintTiming final
   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;
 };