Avoid computing patch_root in get_files_affected_by_patch.

recipe_modules/gclient/example.py

Index: recipe_modules/gclient/example.py
diff --git a/recipe_modules/gclient/example.py b/recipe_modules/gclient/example.py
index fa6daf8950862ab8c919bf525932360496efa0a9..49a4d4b5f325e8dccf403362daa4cab293dc860e 100644
--- a/recipe_modules/gclient/example.py
+++ b/recipe_modules/gclient/example.py
@@ -6,6 +6,7 @@ DEPS = [
   'gclient',
   'recipe_engine/path',
   'recipe_engine/properties',
+  'recipe_engine/platform',
 ]
 
 
@@ -66,6 +67,8 @@ def RunSteps(api):
   src_cfg.parent_got_revision_mapping['parent_got_revision'] = 'got_revision'
   api.gclient.c = src_cfg
   api.gclient.checkout()
+  api.gclient.get_files_affected_by_patch(
+      patch_project=api.properties.get('patch_project'))
 
   api.gclient.spec_alias = 'WebKit'
   bl_cfg = api.gclient.make_config()
@@ -92,9 +95,12 @@ def RunSteps(api):
   assert not api.gclient.is_blink_mode
 
 
+
 def GenTests(api):
   yield api.test('basic')
 
   yield api.test('revision') + api.properties(revision='abc')
 
   yield api.test('tryserver') + api.properties.tryserver()
+  yield (api.test('tryserver_win') + api.properties.tryserver() +
+         api.platform('win', 64))