change offset to xy for pixelref subsetting

include/core/SkBitmapDevice.h

Index: include/core/SkBitmapDevice.h
diff --git a/include/core/SkBitmapDevice.h b/include/core/SkBitmapDevice.h
index f3d40d0ce8d9ca53102fb360b0b76e5cd799e59c..a9208e20a02ac2dbe6c14efb05fd3fd9f0eb310b 100644
--- a/include/core/SkBitmapDevice.h
+++ b/include/core/SkBitmapDevice.h
@@ -199,8 +199,8 @@ protected:
 
     SkPixelRef* getPixelRef() const { return fBitmap.pixelRef(); }
     // just for subclasses, to assign a custom pixelref
-    SkPixelRef* setPixelRef(SkPixelRef* pr, size_t offset) {
-        fBitmap.setPixelRef(pr, offset);
+    SkPixelRef* setPixelRef(SkPixelRef* pr) {
+        fBitmap.setPixelRef(pr);
         return pr;
     }