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 ignoreLCDText) const {
-  if (layer->layoutObject().style()->position() != EPosition::kFixed &&
-      layer->layoutObject().style()->position() != EPosition::kSticky)
+  if (!layer->layoutObject().style()->hasViewportConstrainedPosition() &&
+      !layer->layoutObject().style()->hasStickyConstrainedPosition())
     return false;
 
   if (!(ignoreLCDText ||
         (m_compositingTriggers & ViewportConstrainedPositionedTrigger)) &&
       (!RuntimeEnabledFeatures::compositeOpaqueFixedPositionEnabled() ||
        !layer->backgroundIsKnownToBeOpaqueInRect(
            LayoutRect(layer->boundingBoxForCompositing())) ||
        layer->compositesWithTransform() || layer->compositesWithOpacity())) {
     return false;
   }
@@ skipping 18 matching lines @@
 
   // Don't promote sticky position elements that cannot move with scrolls.
   if (!layer->sticksToScroller())
     return false;
   if (layer->ancestorOverflowLayer()->isRootLayer())
     return m_layoutView.frameView()->isScrollable();
   return layer->ancestorOverflowLayer()->scrollsOverflow();
 }
 
 }  // namespace blink