Change gclient to use the depot_tools module.

recipe_modules/gclient/api.py

Index: recipe_modules/gclient/api.py
diff --git a/recipe_modules/gclient/api.py b/recipe_modules/gclient/api.py
index b52dcd9db9b1869ed7652e6ee4ac95c500b15deb..34b2ebd8334e7375ef8b28dda99e9ab63c88eea2 100644
--- a/recipe_modules/gclient/api.py
+++ b/recipe_modules/gclient/api.py
@@ -91,7 +91,7 @@ class GclientApi(recipe_api.RecipeApi):
       prefix = ('[spec: %s] ' % self.spec_alias) + prefix
 
     return self.m.python(prefix + name,
-                         self.m.path['depot_tools'].join('gclient.py'),
+                         self.m.depot_tools.gclient_py,
                          cmd,
                          infra_step=infra_step,
                          **kwargs)