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

src/effects/SkXfermodeImageFilter.cpp

 /*
  * Copyright 2013 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkXfermodeImageFilter.h"
 #include "SkCanvas.h"
 #include "SkDevice.h"
@@ skipping 70 matching lines @@
     paint.setXfermodeMode(SkXfermode::kSrc_Mode);
     canvas.drawBitmap(background, SkIntToScalar(backgroundOffset.fX),
                       SkIntToScalar(backgroundOffset.fY), &paint);
     paint.setXfermode(fMode);
     canvas.drawBitmap(foreground, SkIntToScalar(foregroundOffset.fX),
                       SkIntToScalar(foregroundOffset.fY), &paint);
     canvas.clipRect(SkRect::Make(foregroundBounds), SkRegion::kDifference_Op);
     paint.setColor(SK_ColorTRANSPARENT);
     canvas.drawPaint(paint);
     *dst = device->accessBitmap(false);
-    offset->fX += bounds.left();
-    offset->fY += bounds.top();
+    offset->fX = bounds.left();
+    offset->fY = bounds.top();
     return true;
 }
 
 #if SK_SUPPORT_GPU
 
 bool SkXfermodeImageFilter::filterImageGPU(Proxy* proxy,
                                            const SkBitmap& src,
                                            const SkMatrix& ctm,
                                            SkBitmap* result,
                                            SkIPoint* offset) {
@@ skipping 47 matching lines @@
         GrPaint backgroundPaint;
         SkMatrix backgroundMatrix = GrEffect::MakeDivByTextureWHMatrix(backgroundTex);
         backgroundPaint.addColorTextureEffect(backgroundTex, backgroundMatrix);
         context->drawRect(backgroundPaint, srcRect);
 
         GrPaint foregroundPaint;
         foregroundPaint.setBlendFunc(sk_blend_to_grblend(sm), sk_blend_to_grblend(dm));
         foregroundPaint.addColorTextureEffect(foregroundTex, foregroundMatrix);
         context->drawRect(foregroundPaint, srcRect);
     }
-    offset->fX += backgroundOffset.fX;
-    offset->fY += backgroundOffset.fY;
+    offset->fX = backgroundOffset.fX;
+    offset->fY = backgroundOffset.fY;
     return SkImageFilterUtils::WrapTexture(dst, src.width(), src.height(), result);
 }
 
 #endif