Add a run_eslint wrapper script

common/eslint/bin/run_eslint

+#!/usr/bin/env python
+# Copyright 2016 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.
+
+import argparse
+import os
+import sys
+
+
+_CATAPULT_PATH = os.path.abspath(
+    os.path.join(os.path.dirname(__file__),
+                 os.path.pardir, os.path.pardir, os.path.pardir))
+
+
+_ESLINT_PATH = os.path.abspath(
+    os.path.join(os.path.dirname(__file__), os.path.pardir))
+
+
+DIRECTORIES_TO_LINT = [
+  os.path.join(_CATAPULT_PATH, 'dashboard', 'dashboard'),
+  os.path.join(_CATAPULT_PATH, 'tracing', 'tracing')
+]
+
+
+def _AddToPathIfNeeded(path):
+  if path not in sys.path:
+    sys.path.insert(0, path)
+
+
+if __name__ == '__main__':
+  _AddToPathIfNeeded(_ESLINT_PATH)
+  import eslint
+
+  parser = argparse.ArgumentParser(
+      description='Wrapper script to run eslint on Catapult code')
+  parser.add_argument('--files', '-f', default=None, nargs='+', metavar='FILE',
+                      help='List of files to lint')
+  parser.add_argument('--all', default=None, action='store_true',
+                      help='Runs eslint on all applicable Catapult code')
+
+  args = parser.parse_args(sys.argv[1:])
+  if ((args.files is not None and args.all is not None) or
+      (args.files is None and args.all is None)):
+    print 'Either --files or --all must be used, but not both.\n'
+    parser.print_help()
+    sys.exit(1)
+
+  if args.all:
+    print eslint.RunEslintOnDirs(DIRECTORIES_TO_LINT)
+  else:
+    print eslint.RunEslintOnFiles(args.files)