Add script tests for `gn check`, `gyp_flag_compare` to GN bot configs.

testing/scripts/gyp_flag_compare.py

Index: testing/scripts/gyp_flag_compare.py
diff --git a/testing/scripts/gyp_flag_compare.py b/testing/scripts/gyp_flag_compare.py
new file mode 100755
index 0000000000000000000000000000000000000000..0b777d9adb1e18c45836d46d4f972d6b6c001676
--- /dev/null
+++ b/testing/scripts/gyp_flag_compare.py
@@ -0,0 +1,49 @@
+#!/usr/bin/env python
+# Copyright 2015 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.
+
+"""Wrap //tools/gn/bin/gyp_flag_compare.py for the bots.
+
+This script wraps the GN test script in the facade needed for the
+'ScriptTest' step class of the chromium recipe_module
+(see scripts/slave/recipe_modules/chromium/steps.py in the build repo.
+
+The script takes N arguments, for the N targets to compare flags for.
+"""
+
+import json
+import os
+import sys
+
+
+import common
+
+
+def main_run(args):
+  rc = common.run_command([sys.executable,
+                           os.path.join(common.SRC_DIR,
+                                        'tools', 'gn', 'bin',
+                                        'gyp_flag_compare.py')] + args.args)
+
+  # TODO(dpranke): Figure out how to get a list of failures out of
+  # gyp_flag_compare?
+  json.dump({
+      'valid': True,
+      'failures': ['compare_failed'] if rc else [],
+  }, args.output)
+
+  return rc
+
+
+def main_compile_targets(args):
+  # TODO(dpranke): Figure out how to get args.args plumbed through to here.
+  json.dump([], args.output)
+
+
+if __name__ == '__main__':
+  funcs = {
+    'run': main_run,
+    'compile_targets': main_compile_targets,
+  }
+  sys.exit(common.run_script(sys.argv[1:], funcs))