[CSS Exclusions] Programmatic layout tests fail when subpixel layout is disabled

LayoutTests/fast/exclusions/resources/simple-polygon.js

 // The functions in this file are intended to be used to test non-complex polygons
 // where horizontal lines that overlap the polygon only cross the polygon twice.
 if (window.internals)
     window.internals.settings.setCSSExclusionsEnabled(true);
 
 function createPolygon(vertices) {
     var xCoordinates = vertices.map( function(p) { return p.x; } );
     var yCoordinates = vertices.map( function(p) { return p.y; } );
     return {
         vertices: vertices,
@@ skipping 71 matching lines @@
             else {
                 interceptsMinX = Math.min(interceptX, interceptsMinX);
                 interceptsMaxX = Math.max(interceptX, interceptsMaxX);
             }
         }
     }
 
     if (!foundXIntercept)
         return [];
 
-    return [SubPixelLayout.roundLineLeft(interceptsMinX), SubPixelLayout.roundLineRight(interceptsMaxX)];
+    return [SubPixelLayout.snapToLayoutUnit(interceptsMinX), SubPixelLayout.snapTolayoutUnit(interceptsMaxX)];
 }
 
 function polygonLineIntercepts(polygon, y, lineHeight) {
     var i1 = polygonXIntercepts(polygon, y);
     var i2 = polygonXIntercepts(polygon, y + lineHeight);
 
     if (i1.length < 2)
         return i2;
     if (i2.length < 2)
         return i1;
@@ skipping 138 matching lines @@
     positionInformativeText("informative-text", stylesheet, polygon, lineHeight)
 }
 
 function createPolygonShapeInsideTestCaseExpected() {
     var stylesheet = document.getElementById("stylesheet").sheet;
     var polygon = createPolygon(vertices);
     generateSimulatedPolygonShapeInsideElement("polygon-shape-inside", stylesheet, polygon, lineHeight);
     generatePolygonSVGElements("polygon-svg-shape", stylesheet, polygon, lineHeight);
     positionInformativeText("informative-text", stylesheet, polygon, lineHeight)
 }