support gpu for skottie2movie

-g will try to render the frames using OpenGL

For the motion-blur test skottie on Mac Pro...

Before: 71.0 secs
After :  6.6 secs

Change-Id: I7e723d4ac0bb63b0e42381ed50bf2144dfc9c8a3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/243428
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index be3bd01..6a17f52 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1826,6 +1826,7 @@
       ]
       deps = [
         ":flags",
+        ":gpu_tool_utils",
         ":skia",
         ":video_decoder",
         "modules/skottie",