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..4fb2a55b99f1d81cbfcab8ee2c3c7831efccf62a
--- /dev/null
+++ b/testing/scripts/gn_check.py
@@ -0,0 +1,56 @@
+#!/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,
+  ])
+
+  json.dump({
+      'valid': True,
+      'failures': [],

[Paweł Hajdan Jr., 2015/05/15 10:14:07]

Do you intend this to always pass? If there are any failures they should be
added to this list.

[Dirk Pranke, 2015/05/15 15:09:40]

I expect the step to fail if rc is nonzero. I don't expect there to be a useful
list of failures (the command is a binary pass/fail, one big test). Do I need to
create some sort of placeholder value anyway?

[Paweł Hajdan Jr., 2015/05/15 15:41:14]

It's expected by recipes that if rc is nonzero there are failures.

We can put some dummy value here for now, but with a TODO to make it real.

+  }, 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))