[SPv2] Track paint offset change

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

Index: third_party/WebKit/Source/core/paint/ObjectPainter.h
diff --git a/third_party/WebKit/Source/core/paint/ObjectPainter.h b/third_party/WebKit/Source/core/paint/ObjectPainter.h
index e73923dfdcf41c19f73defa97d725764cd928469..17d0bd8878651feec24edfe9268c221f53a6e73c 100644
--- a/third_party/WebKit/Source/core/paint/ObjectPainter.h
+++ b/third_party/WebKit/Source/core/paint/ObjectPainter.h
@@ -60,6 +60,13 @@ class ObjectPainter {
   void paintAllPhasesAtomically(const PaintInfo&,
                                 const LayoutPoint& paintOffset);
 
+  void checkPaintOffset(const PaintInfo& paintInfo,

[pdr., 2016/11/10 07:35:32]

Add a comment here:
// SPV2 computes paint offsets during the prepaint tree
// walk (PrePaintTreeWalk). This check verifies that the
// SPV1 paint offset computed during paint matches the
// new SPV2 paint offset.


WDYT about making it more clear at the callsites that this is spv2 debug code?
It's a little verbose but maybe something like:
if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
  DCHECK(ObjectPainter(m_whatever).paintOffsetPrecomputed(paintInfo,
paintOffset));
}

[Xianzhu, 2016/11/10 17:41:10]

Done.
I like the clearness. How about the new patch that moved the checking in header
file?

[pdr., 2016/11/10 18:54:11]

SGTM. Followups are always great.

+                        const LayoutPoint& paintOffset) {
+#if DCHECK_IS_ON()
+    doCheckPaintOffset(paintInfo, paintOffset);
+#endif
+  }
+
  private:
   static void drawDashedOrDottedBoxSide(GraphicsContext&,
                                         int x1,
@@ -105,6 +112,10 @@ class ObjectPainter {
                                int adjacentWidth2,
                                bool antialias);
 
+#if DCHECK_IS_ON()
+  void doCheckPaintOffset(const PaintInfo&, const LayoutPoint& paintOffset);
+#endif
+
   const LayoutObject& m_layoutObject;
 };