antialias matrix-image-filter to get smooth diagonals

src/core/SkMatrixImageFilter.cpp

Index: src/core/SkMatrixImageFilter.cpp
diff --git a/src/core/SkMatrixImageFilter.cpp b/src/core/SkMatrixImageFilter.cpp
index a61867e041a0fad2447f4aa7f9b1468d7a2f95dd..1e76362285c6939ec7e3bcf6e100f64d19370b6f 100644
--- a/src/core/SkMatrixImageFilter.cpp
+++ b/src/core/SkMatrixImageFilter.cpp
@@ -76,13 +76,13 @@ bool SkMatrixImageFilter::onFilterImage(Proxy* proxy,
         return false;
     }
 
+    SkPaint paint;
+    paint.setFilterQuality(fFilterQuality);
+    paint.setAntiAlias(true);   // since we may be rotated, we definitely want a smooth edge
+    
     SkCanvas canvas(device.get());
     canvas.translate(-SkIntToScalar(dstBounds.x()), -SkIntToScalar(dstBounds.y()));
     canvas.concat(matrix);
-    SkPaint paint;
-
-    paint.setXfermodeMode(SkXfermode::kSrc_Mode);
-    paint.setFilterQuality(fFilterQuality);
     canvas.drawBitmap(src, srcRect.x(), srcRect.y(), &paint);
 
     *result = device.get()->accessBitmap(false);