Only create sticky position constraints for constrained sticky position.

third_party/WebKit/Source/core/layout/compositing/CompositingReasonFinder.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/layout/compositing/CompositingReasonFinder.h"
 
 #include "core/CSSPropertyNames.h"
 #include "core/dom/Document.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/Settings.h"
@@ skipping 198 matching lines @@
 bool CompositingReasonFinder::RequiresCompositingForTransformAnimation(
     const ComputedStyle& style) {
   return style.SubtreeWillChangeContents()
              ? style.IsRunningTransformAnimationOnCompositor()
              : style.HasCurrentTransformAnimation();
 }
 
 bool CompositingReasonFinder::RequiresCompositingForScrollDependentPosition(
     const PaintLayer* layer,
     bool ignore_lcd_text) const {
-  if (layer->GetLayoutObject().Style()->GetPosition() != EPosition::kFixed &&
-      layer->GetLayoutObject().Style()->GetPosition() != EPosition::kSticky)
+  if (!layer->GetLayoutObject().Style()->HasViewportConstrainedPosition() &&
+      !layer->GetLayoutObject().Style()->HasStickyConstrainedPosition())
     return false;
 
   if (!(ignore_lcd_text ||
         (compositing_triggers_ & kViewportConstrainedPositionedTrigger)) &&
       (!RuntimeEnabledFeatures::compositeOpaqueFixedPositionEnabled() ||
        !layer->BackgroundIsKnownToBeOpaqueInRect(
            LayoutRect(layer->BoundingBoxForCompositing())) ||
        layer->CompositesWithTransform() || layer->CompositesWithOpacity())) {
     return false;
   }
   // Don't promote fixed position elements that are descendants of a non-view
   // container, e.g. transformed elements.  They will stay fixed wrt the
   // container rather than the enclosing frame.
   EPosition position = layer->GetLayoutObject().Style()->GetPosition();
   if (position == EPosition::kFixed)
     return layer->FixedToViewport() &&
            layout_view_.GetFrameView()->IsScrollable();
   DCHECK_EQ(position, EPosition::kSticky);
 
   // Don't promote sticky position elements that cannot move with scrolls.
   if (!layer->SticksToScroller())
     return false;
   if (layer->AncestorOverflowLayer()->IsRootLayer())
     return layout_view_.GetFrameView()->IsScrollable();
   return layer->AncestorOverflowLayer()->ScrollsOverflow();
 }
 
 }  // namespace blink