ViewPainter should skip painting if not inside painting subtree

Source/core/paint/ViewPainter.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 "config.h"
 #include "core/paint/ViewPainter.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/Settings.h"
 #include "core/layout/LayoutBox.h"
@@ skipping 13 matching lines @@
     ASSERT(!m_layoutView.needsLayout());
     // LayoutViews should never be called to paint with an offset not on device pixels.
     ASSERT(LayoutPoint(IntPoint(paintOffset.x(), paintOffset.y())) == paintOffset);
 
     m_layoutView.paintObject(paintInfo, paintOffset);
     BlockPainter(m_layoutView).paintOverflowControlsIfNeeded(paintInfo, paintOffset);
 }
 
 void ViewPainter::paintBoxDecorationBackground(const PaintInfo& paintInfo)
 {
+    if (!paintInfo.shouldPaintWithinRoot(&m_layoutView))
+        return;
+
     if (paintInfo.skipRootBackground())
         return;
 
     // This function overrides background painting for the LayoutView.
     // View background painting is special in the following ways:
     // 1. The view paints background for the root element, the background positioning respects
     //    the positioning and transformation of the root element.
     // 2. CSS background-clip is ignored, the background layers always expand to cover the whole
     //    canvas. None of the stacking context effects (except transformation) on the root element
     //    affects the background.
@@ skipping 84 matching lines @@
         ASSERT((*it)->clip() == BorderFillBox);
         BoxPainter::paintFillLayerExtended(m_layoutView, paintInfo, Color(), **it, LayoutRect(paintRect), BackgroundBleedNone);
     }
     context.restore();
 
     if (shouldDrawBackgroundInSeparateBuffer)
         context.endLayer();
 }
 
 } // namespace blink