gm: use DEF_GM macro consistantly

Change-Id: I705180db106ec4515aaec5f347199b98b21976fa
Reviewed-on: https://skia-review.googlesource.com/c/186081
Auto-Submit: Hal Canary <halcanary@google.com>
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
diff --git a/gm/dstreadshuffle.cpp b/gm/dstreadshuffle.cpp
index 68dcfc4..fbaac15 100644
--- a/gm/dstreadshuffle.cpp
+++ b/gm/dstreadshuffle.cpp
@@ -182,7 +182,6 @@
 
 //////////////////////////////////////////////////////////////////////////////
 
-static GM* MyFactory(void*) { return new DstReadShuffle; }
-static GMRegistry reg(MyFactory);
+DEF_GM( return new DstReadShuffle; )
 
 }