[CSS Shapes] Simplify RasterShape implementation

Source/core/rendering/shapes/Shape.cpp

 /*
  * Copyright (C) 2012 Adobe Systems Incorporated. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above
  *    copyright notice, this list of conditions and the following
  *    disclaimer.
@@ skipping 184 matching lines @@
         int maxBufferY = std::min(imageRect.height(), marginRect.maxY() - imageRect.y());
 
         for (int y = minBufferY; y < maxBufferY; ++y) {
             int startX = -1;
             for (int x = 0; x < imageRect.width(); ++x, pixelArrayOffset += 4) {
                 uint8_t alpha = pixelArray->item(pixelArrayOffset);
                 bool alphaAboveThreshold = alpha > alphaPixelThreshold;
                 if (startX == -1 && alphaAboveThreshold) {
                     startX = x;
                 } else if (startX != -1 && (!alphaAboveThreshold || x == imageRect.width() - 1)) {
-                    intervals->appendInterval(y + imageRect.y(), startX + imageRect.x(), x + imageRect.x());
+                    intervals->intervalAt(y + imageRect.y()).unite(IntShapeInterval(startX + imageRect.x(), x + imageRect.x()));
                     startX = -1;
                 }
             }
         }
     }
 
     OwnPtr<RasterShape> rasterShape = adoptPtr(new RasterShape(intervals.release(), marginRect.size()));
     rasterShape->m_writingMode = writingMode;
     rasterShape->m_margin = floatValueForLength(margin, 0);
     return rasterShape.release();
 }
 
 PassOwnPtr<Shape> Shape::createLayoutBoxShape(const RoundedRect& roundedRect, WritingMode writingMode, const Length& margin)
 {
     FloatRect rect(0, 0, roundedRect.rect().width(), roundedRect.rect().height());
     FloatRoundedRect bounds(rect, roundedRect.radii());
     OwnPtr<Shape> shape = createInsetShape(bounds);
     shape->m_writingMode = writingMode;
     shape->m_margin = floatValueForLength(margin, 0);
 
     return shape.release();
 }
 
 } // namespace WebCore