Fix the bug that absolute positioned element moves unexpectedly

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 129 matching lines @@
   return layout_object.HasTransformRelatedProperty() &&
          layout_object.StyleRef().Has3DTransform();
 }
 
 CompositingReasons CompositingReasonFinder::NonStyleDeterminedDirectReasons(
     const PaintLayer* layer,
     bool ignore_lcd_text) const {
   CompositingReasons direct_reasons = kCompositingReasonNone;
   LayoutObject& layout_object = layer->GetLayoutObject();
 
-  if (compositing_triggers_ & kOverflowScrollTrigger && layer->ClipParent())
+  if (layer->ClipParent())
     direct_reasons |= kCompositingReasonOutOfFlowClipping;
 
   if (layer->NeedsCompositedScrolling())
     direct_reasons |= kCompositingReasonOverflowScrollingTouch;
 
   // Composite |layer| if it is inside of an ancestor scrolling layer, but that
   // scrolling layer is not on the stacking context ancestor chain of |layer|.
   // See the definition of the scrollParent property in Layer for more detail.
   if (const PaintLayer* scrolling_ancestor = layer->AncestorScrollingLayer()) {
     if (scrolling_ancestor->NeedsCompositedScrolling() && layer->ScrollParent())
@@ skipping 78 matching lines @@
 
   // 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