Snap the positioning area size

third_party/WebKit/Source/core/paint/BackgroundImageGeometry.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 "core/paint/BackgroundImageGeometry.h"
 
 #include "core/frame/FrameView.h"
 #include "core/layout/LayoutBox.h"
 #include "core/layout/LayoutBoxModelObject.h"
 #include "core/layout/LayoutView.h"
@@ skipping 258 matching lines @@
 
     LayoutSize fillTileSize(calculateFillTileSize(positioningBox, fillLayer, positioningAreaSize));
     // It's necessary to apply the heuristic here prior to any further calculations to avoid
     // incorrectly using sub-pixel values that won't be present in the painted tile.
     fillTileSize = applySubPixelHeuristicToImageSize(fillTileSize, m_destRect);
     setTileSize(fillTileSize);
     setImageContainerSize(fillTileSize);
 
     EFillRepeat backgroundRepeatX = fillLayer.repeatX();
     EFillRepeat backgroundRepeatY = fillLayer.repeatY();
+    positioningAreaSize = LayoutSize(snapSizeToPixel(positioningAreaSize.width(), m_destRect.x()), snapSizeToPixel(positioningAreaSize.height(), m_destRect.y()));
     LayoutUnit availableWidth = positioningAreaSize.width() - tileSize().width();
     LayoutUnit availableHeight = positioningAreaSize.height() - tileSize().height();
 
     LayoutUnit computedXPosition = roundedMinimumValueForLength(fillLayer.xPosition(), availableWidth);
     if (backgroundRepeatX == RoundFill && positioningAreaSize.width() > LayoutUnit() && fillTileSize.width() > LayoutUnit()) {
         int nrTiles = std::max(1, roundToInt(positioningAreaSize.width() / fillTileSize.width()));
 
         fillTileSize.setWidth(positioningAreaSize.width() / nrTiles);
 
         // Maintain aspect ratio if background-size: auto is set
@@ skipping 69 matching lines @@
     }
 
     if (fixedAttachment)
         useFixedAttachment(paintRect.location());
 
     clip(paintRect);
     pixelSnapGeometry();
 }
 
 } // namespace blink