Don't include scroll offset in offsetFromLayoutObject for scrolling contents layers.

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

Index: third_party/WebKit/Source/core/layout/LayoutObject.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutObject.cpp b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
index f8198c2d73933106465f52b2e401e5662b67ac88..c877ac8fdcc62c501fefab80ef1922bd106e0aaa 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObject.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
@@ -1223,8 +1223,9 @@ void LayoutObject::invalidatePaintUsingContainer(const LayoutBoxModelObject& pai
     if (!paintInvalidationContainer.isPaintInvalidationContainer())
         invalidatePaintRectangleOnWindow(paintInvalidationContainer, enclosingIntRect(dirtyRect));
 
+    bool compositedScrolling = paintInvalidationContainer.usesCompositedScrolling() && &paintInvalidationContainer != this;

[Xianzhu, 2016/05/31 16:06:20]

You can move this into
LayoutBoxModelObject::setBackingNeedsPaintInvalidationInRect() to avoid the
additional bool parameter.

[chrishtr, 2016/05/31 16:36:43]

Done.

     if (paintInvalidationContainer.view()->usesCompositing() && paintInvalidationContainer.isPaintInvalidationContainer())
-        paintInvalidationContainer.setBackingNeedsPaintInvalidationInRect(dirtyRect, invalidationReason, *this);
+        paintInvalidationContainer.setBackingNeedsPaintInvalidationInRect(dirtyRect, invalidationReason, *this, compositedScrolling);
 }
 
 void LayoutObject::invalidateDisplayItemClient(const DisplayItemClient& displayItemClient) const
@@ -1560,22 +1561,18 @@ void LayoutObject::incrementallyInvalidatePaint(const LayoutBoxModelObject& pain
     LayoutUnit deltaRight = newBounds.maxX() - oldBounds.maxX();
     if (deltaRight > 0) {
         LayoutRect invalidationRect(oldBounds.maxX(), newBounds.y(), deltaRight, newBounds.height());
-        adjustInvalidationRectForCompositedScrolling(invalidationRect, paintInvalidationContainer);
         invalidatePaintUsingContainer(paintInvalidationContainer, invalidationRect, PaintInvalidationIncremental);
     } else if (deltaRight < 0) {
         LayoutRect invalidationRect(newBounds.maxX(), oldBounds.y(), -deltaRight, oldBounds.height());
-        adjustInvalidationRectForCompositedScrolling(invalidationRect, paintInvalidationContainer);
         invalidatePaintUsingContainer(paintInvalidationContainer, invalidationRect, PaintInvalidationIncremental);
     }
 
     LayoutUnit deltaBottom = newBounds.maxY() - oldBounds.maxY();
     if (deltaBottom > 0) {
         LayoutRect invalidationRect(newBounds.x(), oldBounds.maxY(), newBounds.width(), deltaBottom);
-        adjustInvalidationRectForCompositedScrolling(invalidationRect, paintInvalidationContainer);
         invalidatePaintUsingContainer(paintInvalidationContainer, invalidationRect, PaintInvalidationIncremental);
     } else if (deltaBottom < 0) {
         LayoutRect invalidationRect(oldBounds.x(), newBounds.maxY(), oldBounds.width(), -deltaBottom);
-        adjustInvalidationRectForCompositedScrolling(invalidationRect, paintInvalidationContainer);
         invalidatePaintUsingContainer(paintInvalidationContainer, invalidationRect, PaintInvalidationIncremental);
     }
 }
@@ -1585,7 +1582,6 @@ void LayoutObject::fullyInvalidatePaint(const LayoutBoxModelObject& paintInvalid
     // The following logic avoids invalidating twice if one set of bounds contains the other.
     if (!newBounds.contains(oldBounds)) {
         LayoutRect invalidationRect = oldBounds;
-        adjustInvalidationRectForCompositedScrolling(invalidationRect, paintInvalidationContainer);
         invalidatePaintUsingContainer(paintInvalidationContainer, invalidationRect, invalidationReason);
 
         if (oldBounds.contains(newBounds))
@@ -1593,7 +1589,6 @@ void LayoutObject::fullyInvalidatePaint(const LayoutBoxModelObject& paintInvalid
     }
 
     LayoutRect invalidationRect = newBounds;
-    adjustInvalidationRectForCompositedScrolling(invalidationRect, paintInvalidationContainer);
     invalidatePaintUsingContainer(paintInvalidationContainer, invalidationRect, invalidationReason);
 }
 
@@ -3584,7 +3579,6 @@ void LayoutObject::invalidatePaintOfPreviousPaintInvalidationRect(const LayoutBo
     DisableCompositingQueryAsserts compositingDisabler;
 
     LayoutRect invalidationRect = previousPaintInvalidationRect();
-    adjustInvalidationRectForCompositedScrolling(invalidationRect, paintInvalidationContainer);
     invalidatePaintUsingContainer(paintInvalidationContainer, invalidationRect, reason);
     invalidateDisplayItemClients(paintInvalidationContainer, reason);