Fix aspect ratio for rounded background image 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 336 matching lines @@
     EFillRepeat backgroundRepeatY = fillLayer.repeatY();
     LayoutUnit unsnappedAvailableWidth = positioningAreaSize.width() - fillTileSize.width();
     LayoutUnit unsnappedAvailableHeight = positioningAreaSize.height() - fillTileSize.height();
     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);
+        LayoutUnit roundedWidth = positioningAreaSize.width() / nrTiles;
 
         // Maintain aspect ratio if background-size: auto is set
         if (fillLayer.size().size.height().isAuto() && backgroundRepeatY != RoundFill) {
-            fillTileSize.setHeight(fillTileSize.height() * positioningAreaSize.width() / (nrTiles * fillTileSize.width()));
+            fillTileSize.setHeight(fillTileSize.height() * roundedWidth / fillTileSize.width());
         }
+        fillTileSize.setWidth(roundedWidth);
+
         setTileSize(applySubPixelHeuristicToImageSize(fillTileSize, m_destRect));
         setPhaseX(tileSize().width()
             ? LayoutUnit(roundf(tileSize().width() - fmodf((computedXPosition + left), tileSize().width())))
             : LayoutUnit());
         setSpaceSize(LayoutSize());
     }
 
     LayoutUnit computedYPosition = roundedMinimumValueForLength(fillLayer.yPosition(), availableHeight);
     if (backgroundRepeatY == RoundFill && positioningAreaSize.height() > LayoutUnit() && fillTileSize.height() > LayoutUnit()) {
         int nrTiles = std::max(1, roundToInt(positioningAreaSize.height() / fillTileSize.height()));
-
-        fillTileSize.setHeight(positioningAreaSize.height() / nrTiles);
-
+        LayoutUnit roundedHeight = positioningAreaSize.height() / nrTiles;
         // Maintain aspect ratio if background-size: auto is set
         if (fillLayer.size().size.width().isAuto() && backgroundRepeatX != RoundFill) {
-            fillTileSize.setWidth(fillTileSize.width() * positioningAreaSize.height() / (nrTiles * fillTileSize.height()));
+            fillTileSize.setWidth(fillTileSize.width() * roundedHeight / fillTileSize.height());
         }
+        fillTileSize.setHeight(roundedHeight);
+
         setTileSize(applySubPixelHeuristicToImageSize(fillTileSize, m_destRect));
         setPhaseY(tileSize().height()
             ? LayoutUnit(roundf(tileSize().height() - fmodf((computedYPosition + top), tileSize().height())))
             : LayoutUnit());
         setSpaceSize(LayoutSize());
     }
 
     if (backgroundRepeatX == RepeatFill) {
         setRepeatX(fillLayer, fillTileSize.width(), availableWidth, unsnappedAvailableWidth, left);
     } else if (backgroundRepeatX == SpaceFill && tileSize().width() > LayoutUnit()) {
@@ skipping 28 matching lines @@
     // Clip the final output rect to the paint rect
     m_destRect.intersect(paintRect);
 
     // Snap as-yet unsnapped values.
     DCHECK(m_phase == LayoutPoint(roundedIntPoint(m_phase)));
     setDestRect(LayoutRect(pixelSnappedIntRect(m_destRect)));
 
 }
 
 } // namespace blink