Fix leak in multipicturedraw GMs.

R=robertphillips@google.com

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/502493002
diff --git a/gm/multipicturedraw.cpp b/gm/multipicturedraw.cpp
index a030bcc..2da1ab6 100644
--- a/gm/multipicturedraw.cpp
+++ b/gm/multipicturedraw.cpp
@@ -295,8 +295,8 @@
         const SkPicture* fPictures[2];
 
         virtual void onOnceBeforeDraw() SK_OVERRIDE {
-            fPictures[0] = SkRef(make_picture(SK_ColorWHITE));
-            fPictures[1] = SkRef(make_picture(SK_ColorGRAY));
+            fPictures[0] = make_picture(SK_ColorWHITE);
+            fPictures[1] = make_picture(SK_ColorGRAY);
         }
 
         virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE{