Fixed memory leak in bitmaprect GM

https://codereview.appspot.com/6593058/



git-svn-id: http://skia.googlecode.com/svn/trunk@5763 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gm/bitmaprect.cpp b/gm/bitmaprect.cpp
index c438776..4af6f0b 100644
--- a/gm/bitmaprect.cpp
+++ b/gm/bitmaprect.cpp
@@ -201,7 +201,7 @@
 
         SkPaint paint;
         paint.setAlpha(128);
-        paint.setXfermode(mode);
+        paint.setXfermode(mode)->unref();
 
         SkBitmap bitmap;
         make_big_bitmap(&bitmap);