Remove logic about recording style related main thread scroll reasons

third_party/WebKit/Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 5075 matching lines @@
     const {
   MainThreadScrollingReasons reasons =
       static_cast<MainThreadScrollingReasons>(0);
 
   if (shouldThrottleRendering())
     return reasons;
 
   if (hasBackgroundAttachmentFixedObjects())
     reasons |= MainThreadScrollingReason::kHasBackgroundAttachmentFixedObjects;
 
-  reasons |= getStyleRelatedMainThreadScrollingReasons();
-
   ScrollingReasons scrollingReasons = getScrollingReasons();
   const bool mayBeScrolledByInput = (scrollingReasons == Scrollable);
   const bool mayBeScrolledByScript =
       mayBeScrolledByInput ||
       (scrollingReasons == 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.
@@ skipping 153 matching lines @@
 void FrameView::setAnimationHost(
     std::unique_ptr<CompositorAnimationHost> host) {
   m_animationHost = std::move(host);
 }
 
 LayoutUnit FrameView::caretWidth() const {
   return LayoutUnit(getHostWindow()->windowToViewportScalar(1));
 }
 
 }  // namespace blink