Do not promote position sticky or fixed elements unless they move with scroll.

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 333d17dea30e5a45a176685a846d9fb2bab5e21e..c9c31defec8e1b0afdf6181ce78f3c89a97a7076 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -1728,7 +1728,8 @@ bool FrameView::invalidateViewportConstrainedObjects() {
   for (const auto& viewportConstrainedObject : *m_viewportConstrainedObjects) {
     LayoutObject* layoutObject = viewportConstrainedObject;
     LayoutItem layoutItem = LayoutItem(layoutObject);
-    ASSERT(layoutItem.style()->hasViewportConstrainedPosition());
+    DCHECK(layoutItem.style()->hasViewportConstrainedPosition() ||
+           layoutItem.style()->hasStickyConstrainedPosition());
     ASSERT(layoutItem.hasLayer());
     PaintLayer* layer = LayoutBoxModel(layoutItem).layer();
 
@@ -4958,7 +4959,7 @@ bool FrameView::hasVisibleSlowRepaintViewportConstrainedObjects() const {
     // Whether the Layer sticks to the viewport is a tree-depenent
     // property and our viewportConstrainedObjects collection is maintained
     // with only LayoutObject-level information.
-    if (!layer->sticksToViewport())
+    if (!layer->fixedToViewport() && !layer->sticksToScroller())
       continue;
 
     // If the whole subtree is invisible, there's no reason to scroll on