Invalidate fixed-pos elements & descendants on scroll w/filters that change pixels.

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

Index: third_party/WebKit/Source/core/frame/FrameView.cpp
diff --git a/third_party/WebKit/Source/core/frame/FrameView.cpp b/third_party/WebKit/Source/core/frame/FrameView.cpp
index c2bc13f9d104dfbd0107264d59ce9fdebe2ac1a5..e00ae6d5bc5f5f3b2ac07235e10c506310632c29 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -1410,6 +1410,9 @@ bool FrameView::invalidateViewportConstrainedObjects()
         if (layer->subtreeIsInvisible())
             continue;
 
+        // invalidate even if there is an ancestor with a filter that moves pixels.
+        layoutItem.setShouldDoFullPaintInvalidationIncludingNonCompositingDescendants();
+
         // If the fixed layer has a blur/drop-shadow filter applied on at least one of its parents, we cannot
         // scroll using the fast path, otherwise the outsets of the filter will be moved around the page.
         if (layer->hasAncestorWithFilterThatMovesPixels())
@@ -1422,7 +1425,6 @@ bool FrameView::invalidateViewportConstrainedObjects()
             "data",
             InspectorScrollInvalidationTrackingEvent::data(*layoutObject));
 
-        layoutItem.setShouldDoFullPaintInvalidationIncludingNonCompositingDescendants();
     }
     return true;
 }