depot_tools: Remove unused files.

- appengine_mapper.py
- checkout.py
- patch.py
- testing_support/gerrit_test_case.py
- testing_support/patches_data.py
- tests/checkout_test.py
- tests/patch_test.py

Bug: 984182
Change-Id: I2d1ccb1dc41d7034f63043aa87bca3bca4e18294
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1727401Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

appengine_mapper.py

-# Copyright (c) 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.
-
-"""Ensures that all depot_tools talks directly to appengine to avoid SNI."""
-
-import urlparse
-
-
-mapping = {
-  'codereview.chromium.org': 'chromiumcodereview.appspot.com',
-  'crashpad.chromium.org': 'crashpad-home.appspot.com',
-  'bugs.chromium.org': 'monorail-prod.appspot.com',
-  'bugs-staging.chromium.org': 'monorail-staging.appspot.com',
-}
-
-
-def MapUrl(url):
-  parts = list(urlparse.urlsplit(url))
-  new_netloc = mapping.get(parts[1])
-  if new_netloc:
-    parts[1] = new_netloc
-  return urlparse.urlunsplit(parts)

git_cl.py

@@ -40,7 +40,6 @@ import zlib
 from third_party import colorama
 from third_party import httplib2
 import auth
-import checkout
 import clang_format
 import dart_format
 import setup_color

tests/git_cl_test.py

@@ -83,19 +83,6 @@ class PresubmitMock(object):
     return True
 
 
-class GitCheckoutMock(object):
-  def __init__(self, *args, **kwargs):
-    pass
-
-  @staticmethod
-  def reset():
-    GitCheckoutMock.conflict = False
-
-  def apply_patch(self, p):
-    if GitCheckoutMock.conflict:
-      raise Exception('failed')
-
-
 class WatchlistsMock(object):
   def __init__(self, _):
     pass
@@ -673,8 +660,6 @@ class TestGitCl(TestCase):
     self.mock(git_cl, 'write_json', lambda path, contents:
               self._mocked_call('write_json', path, contents))
     self.mock(git_cl.presubmit_support, 'DoPresubmitChecks', PresubmitMock)
-    self.mock(git_cl.checkout, 'GitCheckout', GitCheckoutMock)
-    GitCheckoutMock.reset()
     self.mock(git_cl.watchlists, 'Watchlists', WatchlistsMock)
     self.mock(git_cl.auth, 'get_authenticator_for_host', AuthenticatorMock)
     self.mock(git_cl.gerrit_util, 'GetChangeDetail',