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

testing/scripts/gn_check.py

Index: testing/scripts/gn_check.py
diff --git a/testing/scripts/gn_check.py b/testing/scripts/gn_check.py
new file mode 100755
index 0000000000000000000000000000000000000000..5feb166c5e31278a989bf9b921df0de80cfee44b
--- /dev/null
+++ b/testing/scripts/gn_check.py
@@ -0,0 +1,57 @@
+#!/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 `gn check` for the bots.
+
+This script wraps the `gn check` command 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 no arguments.
+"""
+
+
+import json
+import os
+import sys
+
+
+import common
+
+
+def main_run(args):
+  if sys.platform == 'win32':
+    exe = os.path.join(common.SRC_DIR, 'buildtools', 'win', 'gn.exe')
+  elif sys.platform == 'mac':
+    exe = os.path.join(common.SRC_DIR, 'buildtools', 'mac', 'gn')
+  else:
+    exe = os.path.join(common.SRC_DIR, 'buildtools', 'linux64', 'gn')
+
+  rc = common.run_command([
+      exe,
+      '--root=%s' % common.SRC_DIR,
+      'check',
+      '//out/%s' % args.build_config_fs,
+  ])
+
+  # TODO(dpranke): Figure out how to get a list of failures out of gn check?
+  json.dump({
+      'valid': True,
+      'failures': ['check_failed'] if rc else [],
+  }, args.output)
+
+  return rc
+
+
+def main_compile_targets(args):
+  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))