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

src/effects/SkRectShaderImageFilter.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkRectShaderImageFilter.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
@@ skipping 56 matching lines @@
     }
     SkCanvas canvas(device.get());
     SkPaint paint;
     paint.setShader(fShader);
     SkMatrix matrix;
     matrix.setTranslate(-SkIntToScalar(bounds.fLeft), -SkIntToScalar(bounds.fTop));
     fShader->setLocalMatrix(matrix);
     SkRect rect = SkRect::MakeWH(SkIntToScalar(bounds.width()), SkIntToScalar(bounds.height()));
     canvas.drawRect(rect, paint);
     *result = device.get()->accessBitmap(false);
-    offset->fX += bounds.fLeft;
-    offset->fY += bounds.fTop;
+    offset->fX = bounds.fLeft;
+    offset->fY = bounds.fTop;
     return true;
 }