Compensate for source scaling in hidpi mode

third_party/WebKit/Source/core/paint/NinePieceImageGrid.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/NinePieceImageGrid.h"
 
 #include "core/style/ComputedStyle.h"
 #include "core/style/NinePieceImage.h"
 #include "platform/LengthFunctions.h"
 #include "platform/geometry/FloatSize.h"
@@ skipping 208 matching lines @@
             middleScaleFactor.setWidth((float) destinationSize.width() / sourceSize.width());
 
         if (m_verticalTileRule == (Image::TileRule)StretchImageRule)
             middleScaleFactor.setHeight((float) destinationSize.height() / sourceSize.height());
     }
 
     drawInfo.tileScale = middleScaleFactor;
     drawInfo.tileRule = { m_horizontalTileRule, m_verticalTileRule };
 }
 
-NinePieceImageGrid::NinePieceDrawInfo NinePieceImageGrid::getNinePieceDrawInfo(NinePiece piece) const
+NinePieceImageGrid::NinePieceDrawInfo NinePieceImageGrid::getNinePieceDrawInfo(NinePiece piece, float imageScaleFactor) const
 {
+    DCHECK_NE(imageScaleFactor, 0);
+
     NinePieceDrawInfo drawInfo;
     drawInfo.isCornerPiece =
         piece == TopLeftPiece || piece == TopRightPiece || piece == BottomLeftPiece || piece == BottomRightPiece;
 
     if (drawInfo.isCornerPiece)
         setDrawInfoCorner(drawInfo, piece);
     else if (piece != MiddlePiece)
         setDrawInfoEdge(drawInfo, piece);
     else
         setDrawInfoMiddle(drawInfo);
 
+    if (imageScaleFactor != 1) {
+        // The nine piece grid is computed in unscaled image coordinates but must be drawn using
+        // scaled image coordinates.
+        drawInfo.source.scale(imageScaleFactor);
+
+        // Compensate for source scaling by scaling down the individual tiles.
+        drawInfo.tileScale.scale(1 / imageScaleFactor);
+    }
+
     return drawInfo;
 }
 
 } // namespace blink