[SPv2] Track paint offset change

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 a659ba9175ce51d228f2ce460454b97dd2e5b522..5881d845e45fac5c34f56ae08fbc48f062c57301 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObject.h
+++ b/third_party/WebKit/Source/core/layout/LayoutObject.h
@@ -1584,6 +1584,10 @@ 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   // Called when the previous visual rect(s) is no longer valid.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;
+  }
+
   // Only adjusts if the paint invalidation container is not a composited
   // scroller.
   void adjustPreviousPaintInvalidationForScrollIfNeeded(
@@ -1679,6 +1683,9 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
     void setPreviousVisualRect(const LayoutRect& r) {
       m_layoutObject.setPreviousVisualRect(r);
     }
+    void setPreviousPaintOffset(const LayoutPoint& p) {
+      m_layoutObject.m_previousPaintOffset = p;

[chrishtr, 2016/11/10 18:42:00]

DCHECK(slimmingPaintV2Enabled())

[Xianzhu, 2016/11/10 22:51:50]

Added DCHECK(slimmingPaintInvalidationEnabled()). This is also used to track
paint offset change for partial paint property tree update on SPv1.

+    }
     void setHasPreviousLocationInBacking(bool b) {
       m_layoutObject.m_bitfields.setHasPreviousLocationInBacking(b);
     }
@@ -2343,10 +2350,15 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
   // Store state between styleWillChange and styleDidChange
   static bool s_affectsParentBlock;
 
-  // This stores the visual rect from the previous frame. This rect does *not*
-  // account for composited scrolling. See
+  // This stores the visual rect computed by the latest paint invalidation.
+  // This rect does *not* account for composited scrolling. See
   // adjustVisualRectForCompositedScrolling().
   LayoutRect m_previousVisualRect;
+
+  // This stores the paint offset computed by the latest paint property tree
+  // building. It is relative to the containing transform space. It is the same
+  // offset that will be used to paint the object on SPv2.
+  LayoutPoint m_previousPaintOffset;
 };
 
 // FIXME: remove this once the layout object lifecycle ASSERTS are no longer