Add "threaded scrolling disabled" main thread scrolling reason [spv2]

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp

 // Copyright 2015 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/paint/PaintPropertyTreeBuilder.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/layout/LayoutInline.h"
@@ skipping 317 matching lines @@
             }
         }
     }
 
     if (ObjectPaintProperties* properties = object.getMutableForPainting().objectPaintProperties())
         properties->clearScrollbarPaintOffset();
 }
 
 void PaintPropertyTreeBuilder::updateMainThreadScrollingReasons(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
+    if (context.current.scroll && !object.document().settings()->threadedScrollingEnabled())
+        context.current.scroll->addMainThreadScrollingReasons(MainThreadScrollingReason::kThreadedScrollingDisabled);
+
     if (object.isBackgroundAttachmentFixedObject()) {
         auto* scrollNode = context.current.scroll;
         while (scrollNode && !scrollNode->hasMainThreadScrollingReasons(MainThreadScrollingReason::kHasBackgroundAttachmentFixedObjects)) {
             scrollNode->addMainThreadScrollingReasons(MainThreadScrollingReason::kHasBackgroundAttachmentFixedObjects);
             scrollNode = scrollNode->parent();
         }
     }
 }
 
 void PaintPropertyTreeBuilder::updateOverflowClip(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
@@ skipping 222 matching lines @@
         return;
 
     updateOverflowClip(object, context);
     updatePerspective(object, context);
     updateSvgLocalToBorderBoxTransform(object, context);
     updateScrollAndScrollTranslation(object, context);
     updateOutOfFlowContext(object, context);
 }
 
 } // namespace blink