Docserver: Add support for viewing docs with a codereview patch applied

chrome/common/extensions/docs/server2/test_patcher.py

+# Copyright 2013 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 future import Future
+from patcher import Patcher
+
+class TestPatcher(Patcher):
+  def __init__(self, version, patched_files, patch_data, assert_binary=False):
+    self._version = version
+    self._patched_files = patched_files
+    self._patch_data = patch_data
+    self._assert_binary = assert_binary
+
+    self.get_version_count = 0
+    self.get_patched_files_count = 0
+    self.apply_count = 0
+
+  def GetVersion(self):
+    self.get_version_count += 1
+    return self._version
+
+  def GetPatchedFiles(self, version=None):
+    self.get_patched_files_count += 1
+    return self._patched_files
+
+  def Apply(self, paths, file_system, binary, version=None):
+    if self._assert_binary:
+      assert binary
+    self.apply_count += 1
+    try:
+      return Future(value={path: self._patch_data[path] for path in paths})
+    except KeyError:
+      raise FileNotFoundError('One of %s is deleted in the patch.' % paths)