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 2b72207b3fd49b4feb498c3963e23d625b9b2b3b..675f1c02d1a881db52e732a89d1429ee9bb82fff 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -1397,10 +1397,8 @@ bool FrameView::invalidateViewportConstrainedObjects()
         if (layer->subtreeIsInvisible())
             continue;
 
-        // 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())
-            return false;
+        // invalidate even if there is an ancestor with a filter that moves pixels.
+        layoutItem.setShouldDoFullPaintInvalidationIncludingNonCompositingDescendants();
 
         TRACE_EVENT_INSTANT1(
             TRACE_DISABLED_BY_DEFAULT("devtools.timeline.invalidationTracking"),
@@ -1409,7 +1407,10 @@ bool FrameView::invalidateViewportConstrainedObjects()
             "data",
             InspectorScrollInvalidationTrackingEvent::data(*layoutObject));
 
-        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())
+            return false;
     }
     return true;
 }