Combine LayoutObject::previousPaintOffset and paintOffset in paint properties

third_party/WebKit/Source/core/layout/LayoutObject.h

Index: third_party/WebKit/Source/core/layout/LayoutObject.h
diff --git a/third_party/WebKit/Source/core/layout/LayoutObject.h b/third_party/WebKit/Source/core/layout/LayoutObject.h
index 82075ad1ed24a2aa9211a8441f7cc133f7729b22..acf790de9e321718594748c25410df02a120073c 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObject.h
+++ b/third_party/WebKit/Source/core/layout/LayoutObject.h
@@ -1575,9 +1575,7 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
   // Called when the previous visual rect(s) is no longer valid.
   virtual void clearPreviousVisualRects();
 
-  const LayoutPoint& previousPaintOffset() const {
-    return m_previousPaintOffset;
-  }
+  const LayoutPoint& paintOffset() const { return m_paintOffset; }
 
   PaintInvalidationReason fullPaintInvalidationReason() const {
     return m_bitfields.fullPaintInvalidationReason();
@@ -1676,12 +1674,16 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
       m_layoutObject.ensureIsReadyForPaintInvalidation();
     }
 
+    // The following setters store the current values as calculated during the
+    // pre-paint tree walk. TODO(wangxianzhu): Add check of lifecycle states.

[Xianzhu, 2017/01/06 19:24:18]

The TODO means I'm not sure for now if we can check the lifecycle state in all
methods, especially when we still support non-spinvalidation. I feel that we
could change MutableForPainting to MutableForPrePaint and check lifecycle state
in the constructor, but not sure either for now.

[pdr., 2017/01/06 19:40:01]

SGTM

What about the paintOffset accessor (line 1578)? Can we DCHECK in there too?

[Xianzhu, 2017/01/06 22:12:18]

I would like to defer the decision to the TODO. For now there is no harm to
access paintOffset().

     void setPreviousVisualRect(const LayoutRect& r) {
       m_layoutObject.setPreviousVisualRect(r);
     }
-    void setPreviousPaintOffset(const LayoutPoint& p) {
+    void setPaintOffset(const LayoutPoint& p) {
       DCHECK(RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled());
-      m_layoutObject.m_previousPaintOffset = p;
+      DCHECK_EQ(m_layoutObject.document().lifecycle().state(),
+                DocumentLifecycle::InPrePaint);
+      m_layoutObject.m_paintOffset = p;
     }
     void setHasPreviousLocationInBacking(bool b) {
       m_layoutObject.m_bitfields.setHasPreviousLocationInBacking(b);
@@ -1695,6 +1697,7 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
     void setPreviousBackgroundObscured(bool b) {
       m_layoutObject.setPreviousBackgroundObscured(b);
     }
+
     void clearPreviousVisualRects() {
       m_layoutObject.clearPreviousVisualRects();
     }
@@ -2445,7 +2448,7 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
   // offset that will be used to paint the object on SPv2. It's used to detect
   // paint offset change for paint invalidation on SPv2, and partial paint
   // property tree update for SlimmingPaintInvalidation on SPv1 and SPv2.
-  LayoutPoint m_previousPaintOffset;
+  LayoutPoint m_paintOffset;
 
   // For SPv2 only. The ObjectPaintProperties structure holds references to the
   // property tree nodes that are created by the layout object for painting.