shutil recipe_module: port chromium_utils rmtree implementation.

recipe_modules/shutil/api.py

Index: recipe_modules/shutil/api.py
diff --git a/recipe_modules/shutil/api.py b/recipe_modules/shutil/api.py
index 05814de34fa8bdf527376f0abdd866f3becc2a20..8b601acd1cd666794d85145fa1e05564225ffb5f 100644
--- a/recipe_modules/shutil/api.py
+++ b/recipe_modules/shutil/api.py
@@ -7,6 +7,14 @@ from recipe_engine import recipe_api
 class ShutilApi(recipe_api.RecipeApi):
   def rmtree(self, path, **kwargs):
     name = kwargs.pop('name', 'rmtree %s' % path)
+    if kwargs.pop('flag_smart_rmtree', False):
+      # TODO(tandrii): remove this flag and makes this the only implementation.
+      self.m.python(
+          name,
+          self.resource('rmtree.py'),
+          args=[path],
+          **kwargs)
+      return
     self.m.python.inline(
         name,
         """