Switch to null root property tree nodes [spv2]

third_party/WebKit/Source/core/paint/PrePaintTreeWalk.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/PrePaintTreeWalk.h"
 
 #include "core/dom/DocumentLifecycle.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/layout/LayoutMultiColumnSpannerPlaceholder.h"
@@ skipping 11 matching lines @@
 
     PaintPropertyTreeBuilderContext treeBuilderContext;
     PaintInvalidatorContext paintInvalidatorContext;
 };
 
 void PrePaintTreeWalk::walk(FrameView& rootFrame)
 {
     DCHECK(rootFrame.frame().document()->lifecycle().state() == DocumentLifecycle::InPrePaint);
 
     PrePaintTreeWalkContext rootContext;
-    m_propertyTreeBuilder.buildTreeRootNodes(rootFrame, rootContext.treeBuilderContext);
     walk(rootFrame, rootContext);
     m_paintInvalidator.processPendingDelayedPaintInvalidations();
 }
 
 void PrePaintTreeWalk::walk(FrameView& frameView, const PrePaintTreeWalkContext& context)
 {
     if (frameView.shouldThrottleRendering())
         return;
 
     PrePaintTreeWalkContext localContext(context);
@@ skipping 31 matching lines @@
         if (widget && widget->isFrameView()) {
             localContext.treeBuilderContext.current.paintOffset += layoutPart.replacedContentRect().location() - widget->frameRect().location();
             localContext.treeBuilderContext.current.paintOffset = roundedIntPoint(localContext.treeBuilderContext.current.paintOffset);
             walk(*toFrameView(widget), localContext);
         }
         // TODO(pdr): Investigate RemoteFrameView (crbug.com/579281).
     }
 }
 
 } // namespace blink