Make SkImageFilter crop rects relative to the primitive origin, instead of relative to their parent

src/effects/SkBitmapSource.cpp

Index: src/effects/SkBitmapSource.cpp
diff --git a/src/effects/SkBitmapSource.cpp b/src/effects/SkBitmapSource.cpp
index b5ee1dd83464bc9087a33d340a0928bf568db6bf..e75da613eaf9c038590f42d9591df71777df1510 100644
--- a/src/effects/SkBitmapSource.cpp
+++ b/src/effects/SkBitmapSource.cpp
@@ -73,7 +73,7 @@ bool SkBitmapSource::onFilterImage(Proxy* proxy, const SkBitmap&, const SkMatrix
     canvas.drawBitmapRectToRect(fBitmap, &fSrcRect, dstRect, &paint);
 
     *result = device.get()->accessBitmap(false);
-    offset->fX += dstIRect.fLeft;
-    offset->fY += dstIRect.fTop;
+    offset->fX = dstIRect.fLeft;
+    offset->fY = dstIRect.fTop;
     return true;
 }