Add pixel diff to list of recognized tasks

BUG=skia:6778

Change-Id: I61a9562930516f88e1f6308d9a36eda4978f129a
Reviewed-on: https://skia-review.googlesource.com/20600
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Ravi Mistry <rmistry@google.com>
diff --git a/ct/go/ctfe/task_types/task_types.go b/ct/go/ctfe/task_types/task_types.go
index 3059246..c87b067 100644
--- a/ct/go/ctfe/task_types/task_types.go
+++ b/ct/go/ctfe/task_types/task_types.go
@@ -11,6 +11,7 @@
 	"go.skia.org/infra/ct/go/ctfe/chromium_builds"
 	"go.skia.org/infra/ct/go/ctfe/chromium_perf"
 	"go.skia.org/infra/ct/go/ctfe/lua_scripts"
+	"go.skia.org/infra/ct/go/ctfe/pixel_diff"
 	"go.skia.org/infra/ct/go/ctfe/task_common"
 )
 
@@ -19,6 +20,7 @@
 	return []task_common.Task{
 		&chromium_analysis.DBTask{},
 		&chromium_perf.DBTask{},
+		&pixel_diff.DBTask{},
 		&capture_skps.DBTask{},
 		&lua_scripts.DBTask{},
 		&chromium_builds.DBTask{},