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..bfcdeb388f25fe2b341d03b116e06be213a63528 100644
--- a/include/core/SkBitmapDevice.h
+++ b/include/core/SkBitmapDevice.h
@@ -199,11 +199,17 @@ 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;
     }
 
+#if 0
+    SkPixelRef* setPixelRef(SkPixelRef* pr, int dx, int dy) {
+        fBitmap.setPixelRef(pr, dx, dy);
+        return pr;
+    }
+#endif
     /**
      * Implements readPixels API. The caller will ensure that:
      *  1. bitmap has pixel config kARGB_8888_Config.