Add initial prototype for the GN meta-buildsystem.

tools/gn/secondary/third_party/modp_b64/BUILD.gn

Index: tools/gn/secondary/third_party/modp_b64/BUILD.gn
diff --git a/chrome/test/chromeos/autotest/files/client/deps/perf_data_dep/control b/tools/gn/secondary/third_party/modp_b64/BUILD.gn
similarity index 58%
copy from chrome/test/chromeos/autotest/files/client/deps/perf_data_dep/control
copy to tools/gn/secondary/third_party/modp_b64/BUILD.gn
index b82ddd8262b04b4a658c0c7c05a6aaefb9c626a8..5598f12f18209f028e7108ac5a9101e99343854c 100644
--- a/chrome/test/chromeos/autotest/files/client/deps/perf_data_dep/control
+++ b/tools/gn/secondary/third_party/modp_b64/BUILD.gn
@@ -1,5 +1,11 @@
-# Copyright (c) 2013 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-job.setup_dep(['perf_data_dep'])
+# Copyright (c) 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+static_library("modp_b64") {
+  sources = [
+    "modp_b64.cc",
+    "modp_b64.h",
+    "modp_b64_data.h",
+  ]
+}