Add git_cl recipe module.

recipe_modules/git_cl/api.py

+# 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.
+
+from recipe_engine import recipe_api
+
+class GitClApi(recipe_api.RecipeApi):
+  def __call__(self, subcmd, args, name=None, **kwargs):
+    if not name:
+      name = 'git_cl ' + subcmd
+    if 'cwd' not in kwargs:
+      kwargs['cwd'] = (self.c and self.c.repo_location) or None
+
+    return self.m.step(
+        name, [self.package_repo_resource('git_cl.py')] + args, **kwargs)
+
+  def get_description(self, **kwargs):
+    return self('description', ['-d'], stdout=self.m.raw_io.output(), **kwargs)
+
+  def set_description(self, description, **kwargs):
+    return self(
+        'description', ['-n', '-'],
+        stdout=self.m.raw_io.output(),
+        stdin=self.m.raw_io.input(data=description),
+        name='git_cl set description', **kwargs)