Add animating blur image filter GM/slide/bench

Probably still worth having but I haven't been able to reproduce the perf regression in 
crbug.com/668179 with it yet.

Change-Id: If3b0f2998ff38a17a173895ed9cea6950a81f6b7
Reviewed-on: https://skia-review.googlesource.com/5382
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/gn/gm.gni b/gn/gm.gni
index 4732e03..66bc3aa 100644
--- a/gn/gm.gni
+++ b/gn/gm.gni
@@ -15,6 +15,7 @@
   "$_gm/all_bitmap_configs.cpp",
   "$_gm/alphagradients.cpp",
   "$_gm/animatedGif.cpp",
+  "$_gm/animatedimageblurs.cpp",
   "$_gm/anisotropic.cpp",
   "$_gm/annotated_text.cpp",
   "$_gm/arcofzorro.cpp",