Activate FuzzDDLThreading

This was landed but not turned on. D'oh!

Bug: skia:10286
Change-Id: I65682370046c87c854d806253db32795ef3a9d14
Cq-Include-Trybots: luci.skia.skia.primary:Fuzz-Debian10-Clang
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/375736
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Adlai Holler <adlai@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index 497af01..1bdc96e 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -2950,6 +2950,14 @@
       deps = []
     }
 
+    libfuzzer_app("api_ddl_threading") {
+      sources = [
+        "fuzz/FuzzDDLThreading.cpp",
+        "fuzz/oss_fuzz/FuzzDDLThreading.cpp",
+      ]
+      deps = []
+    }
+
     libfuzzer_app("api_gradients") {
       sources = [
         "fuzz/FuzzGradients.cpp",
diff --git a/fuzz/FuzzMain.cpp b/fuzz/FuzzMain.cpp
index 8538a7c..c121ef9 100644
--- a/fuzz/FuzzMain.cpp
+++ b/fuzz/FuzzMain.cpp
@@ -265,6 +265,7 @@
 static std::map<std::string, std::string> cf_api_map = {
     {"api_create_ddl", "CreateDDL"},
     {"api_draw_functions", "DrawFunctions"},
+    {"api_ddl_threading", "DDLThreadingGL"},
     {"api_gradients", "Gradients"},
     {"api_image_filter", "ImageFilter"},
     {"api_mock_gpu_canvas", "MockGPUCanvas"},
diff --git a/fuzz/oss_fuzz/FuzzDDLThreading.cpp b/fuzz/oss_fuzz/FuzzDDLThreading.cpp
new file mode 100644
index 0000000..cda9f0f
--- /dev/null
+++ b/fuzz/oss_fuzz/FuzzDDLThreading.cpp
@@ -0,0 +1,19 @@
+/*
+ * Copyright 2021 Google, LLC
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "fuzz/Fuzz.h"
+
+void fuzz_DDLThreadingGL(Fuzz* f);
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+    if (size > 4000) {
+        return 0;
+    }
+    auto fuzz = Fuzz(SkData::MakeWithoutCopy(data, size));
+    fuzz_DDLThreadingGL(&fuzz);
+    return 0;
+}