depot_tools: expose path to gn.py

recipe_modules/depot_tools/api.py

Index: recipe_modules/depot_tools/api.py
diff --git a/recipe_modules/depot_tools/api.py b/recipe_modules/depot_tools/api.py
index b73cd580ffb43db96d30d9353a56361a9226fd98..edebb9333564d588f6ecab4eaae64e3eac8027b8 100644
--- a/recipe_modules/depot_tools/api.py
+++ b/recipe_modules/depot_tools/api.py
@@ -10,6 +10,10 @@ class DepotToolsApi(recipe_api.RecipeApi):
     return self.package_repo_resource('download_from_google_storage.py')
 
   @property
+  def gn_py_path(self):
+    return self.package_repo_resource('gn.py')
+
+  @property
   def gsutil_py_path(self):
     return self.package_repo_resource('gsutil.py')