Add more specific metrics for main thread scrolling reasons

third_party/WebKit/Source/core/frame/FrameView.h

 /*
    Copyright (C) 1997 Martin Jones (mjones@kde.org)
              (C) 1998 Waldo Bastian (bastian@kde.org)
              (C) 1998, 1999 Torben Weis (weis@kde.org)
              (C) 1999 Lars Knoll (knoll@kde.org)
              (C) 1999 Antti Koivisto (koivisto@kde.org)
    Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights
    reserved.
 
    This library is free software; you can redistribute it and/or
@@ skipping 749 matching lines @@
   void enqueueScrollAnchoringAdjustment(ScrollableArea*);
   void performScrollAnchoringAdjustments();
 
   // For PaintInvalidator temporarily. TODO(wangxianzhu): Move into
   // PaintInvalidator.
   void invalidatePaintIfNeeded(const PaintInvalidationState&);
 
   // Only for SPv2.
   std::unique_ptr<JSONObject> compositedLayersAsJSON(LayerTreeFlags);
 
+  inline int reasonIndex(uint32_t reason) const {

[bokan, 2016/12/13 14:38:57]

inline unneeded, this is inline by virtue of being defined in the class
declaration.

[bokan, 2016/12/13 14:38:57]

This should move as a helper into MainThreadScrollingReason.h

[yigu, 2016/12/13 20:54:10]

Done.

[yigu, 2016/12/13 20:54:10]

Done.

+    if (!reason || reason & (reason - 1))
+      return 0;
+    int power = 0;
+    while (reason > 0) {
+      reason = reason >> 1;
+      ++power;
+    }
+    return power;
+  }
+
+  void adjustMainThreadReasonsDueToLayoutObject(uint32_t reason, bool increase);

[bokan, 2016/12/13 14:38:56]

IMO, this should be called adjustMainThreadReasons or
adjustMainThreadReasonsFromStyle

[yigu, 2016/12/13 20:54:10]

Done.

+
+  MainThreadScrollingReasons checkMainThreadScrollingReasonDueToLayoutObject();

[bokan, 2016/12/13 14:38:56]

check->get, Reason->Reasons

[yigu, 2016/12/13 20:54:10]

Done.

+
  protected:
   // Scroll the content via the compositor.
   bool scrollContentsFastPath(const IntSize& scrollDelta);
 
   // Scroll the content by invalidating everything.
   void scrollContentsSlowPath();
 
   ScrollBehavior scrollBehaviorStyle() const override;
 
   void scrollContentsIfNeeded();
@@ skipping 345 matching lines @@
   struct ObjectPaintInvalidation {
     String name;
     PaintInvalidationReason reason;
   };
   std::unique_ptr<Vector<ObjectPaintInvalidation>>
       m_trackedObjectPaintInvalidations;
 
   // For Slimming Paint v2 only.
   std::unique_ptr<PaintController> m_paintController;
   std::unique_ptr<PaintArtifactCompositor> m_paintArtifactCompositor;
+
+  // For recording main thread scrolling reasons
+  // due to layout object properties. e.g. opacity, transform.
+  // The size of the vector depends on the number of
+  // main thread scrolling reasons.
+  Vector<int> m_mainThreadScrollingReasonLayoutCounter;

[bokan, 2016/12/13 14:38:57]

My read is that this vector is tracking scrolling reasons for all scrollers in a
FrameView (other than the FrameView itself) and they all get combined together
for a page-wide bitmask. In which case this doesn't belong here (we're trying to
remove scrolling from FrameView anyway, so it wouldn't belong here in any case).
Perhaps this should just be in ScrollingCoordinator itself, globally, for the
whole page.

[yigu, 2016/12/13 20:54:10]

Done.

 };
 
 inline void FrameView::incrementVisuallyNonEmptyCharacterCount(unsigned count) {
   if (m_isVisuallyNonEmpty)
     return;
   m_visuallyNonEmptyCharacterCount += count;
   // Use a threshold value to prevent very small amounts of visible content from
   // triggering didMeaningfulLayout.  The first few hundred characters rarely
   // contain the interesting content of the page.
   static const unsigned visualCharacterThreshold = 200;
@@ skipping 20 matching lines @@
                   widget.isFrameView());
 DEFINE_TYPE_CASTS(FrameView,
                   ScrollableArea,
                   scrollableArea,
                   scrollableArea->isFrameView(),
                   scrollableArea.isFrameView());
 
 }  // namespace blink
 
 #endif  // FrameView_h