Implement position: sticky updates on compositor

third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 1019 matching lines @@
         // calculations below.
         if (toLocalFrame(frame)->localFrameRoot() != m_page->mainFrame())
             continue;
 
         FrameView* frameView = toLocalFrame(frame)->view();
         if (!frameView || frameView->shouldThrottleRendering())
             continue;
 
         if (frameView->hasBackgroundAttachmentFixedObjects())
             reasons |= MainThreadScrollingReason::kHasBackgroundAttachmentFixedObjects;
-        if (frameView->hasStickyPositionObjects())
-            reasons |= MainThreadScrollingReason::kHasStickyPositionObjects;
         FrameView::ScrollingReasons scrollingReasons = frameView->getScrollingReasons();
         const bool mayBeScrolledByInput = (scrollingReasons == FrameView::Scrollable);
         const bool mayBeScrolledByScript = mayBeScrolledByInput || (scrollingReasons ==
             FrameView::NotScrollableExplicitlyDisabled);
 
         // TODO(awoloszyn) Currently crbug.com/304810 will let certain
         // overflow:hidden elements scroll on the compositor thread, so we should
         // not let this move there path as an optimization, when we have slow-repaint
         // elements.
         if (mayBeScrolledByScript && hasVisibleSlowRepaintViewportConstrainedObjects(frameView)) {
@@ skipping 22 matching lines @@
     bool frameIsScrollable = frameView && frameView->isScrollable();
     if (frameIsScrollable != m_wasFrameScrollable)
         return true;
 
     if (WebLayer* scrollLayer = frameView ? toWebLayer(frameView->layerForScrolling()) : nullptr)
         return WebSize(frameView->contentsSize()) != scrollLayer->bounds();
     return false;
 }
 
 } // namespace blink