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

src/effects/SkTileImageFilter.cpp

Index: src/effects/SkTileImageFilter.cpp
diff --git a/src/effects/SkTileImageFilter.cpp b/src/effects/SkTileImageFilter.cpp
index 73e5304adb3db2f8a0a87908a5f3e1b0c0d76030..08dfec4493d51d34de9f889a4953ddbb75d604a1 100644
--- a/src/effects/SkTileImageFilter.cpp
+++ b/src/effects/SkTileImageFilter.cpp
@@ -19,15 +19,17 @@ bool SkTileImageFilter::onFilterImage(Proxy* proxy, const SkBitmap& src, const S
                                       SkBitmap* dst, SkIPoint* offset) {
     SkBitmap source = src;
     SkImageFilter* input = getInput(0);
-    SkIPoint localOffset = SkIPoint::Make(0, 0);
-    if (input && !input->filterImage(proxy, src, ctm, &source, &localOffset)) {
+    SkIPoint srcOffset = SkIPoint::Make(0, 0);
+    if (input && !input->filterImage(proxy, src, ctm, &source, &srcOffset)) {
         return false;
     }
 
     SkRect dstRect;
     ctm.mapRect(&dstRect, fDstRect);
-    int w = SkScalarCeilToInt(dstRect.width());
-    int h = SkScalarCeilToInt(dstRect.height());
+    SkIRect dstIRect;
+    dstRect.roundOut(&dstIRect);
+    int w = dstIRect.width();
+    int h = dstIRect.height();
     if (!fSrcRect.width() || !fSrcRect.height() || !w || !h) {
         return false;
     }
@@ -36,10 +38,13 @@ bool SkTileImageFilter::onFilterImage(Proxy* proxy, const SkBitmap& src, const S
     ctm.mapRect(&srcRect, fSrcRect);
     SkIRect srcIRect;
     srcRect.roundOut(&srcIRect);
+    srcIRect.offset(-srcOffset);
     SkBitmap subset;
     SkIRect bounds;
     source.getBounds(&bounds);
+
     if (!srcIRect.intersect(bounds)) {
+        offset->fX = offset->fY = 0;
         return true;
     } else if (!source.extractSubset(&subset, srcIRect)) {
         return false;
@@ -55,10 +60,16 @@ bool SkTileImageFilter::onFilterImage(Proxy* proxy, const SkBitmap& src, const S
 
     SkAutoTUnref<SkShader> shader(SkShader::CreateBitmapShader(subset,
                                   SkShader::kRepeat_TileMode, SkShader::kRepeat_TileMode));
+    SkMatrix shaderMatrix;
+    shaderMatrix.setTranslate(SkIntToScalar(srcOffset.fX),
+                              SkIntToScalar(srcOffset.fY));
+    shader->setLocalMatrix(shaderMatrix);
     paint.setShader(shader);
-    dstRect.offset(SkIntToScalar(localOffset.fX), SkIntToScalar(localOffset.fY));
+    canvas.translate(-dstRect.fLeft, -dstRect.fTop);
     canvas.drawRect(dstRect, paint);
     *dst = device->accessBitmap(false);
+    offset->fX = dstIRect.fLeft;
+    offset->fY = dstIRect.fTop;
     return true;
 }