Reland "Skia: Maintain a checkout on swarming (compile) bots"

scripts/slave/recipe_modules/skia_swarming/api.py

Index: scripts/slave/recipe_modules/skia_swarming/api.py
diff --git a/scripts/slave/recipe_modules/skia_swarming/api.py b/scripts/slave/recipe_modules/skia_swarming/api.py
index 275f2d35a91555c90f8dd9a9d720625e9fa144ba..950cc9d069abbe0bc0cff872538485a5a2fb7add 100644
--- a/scripts/slave/recipe_modules/skia_swarming/api.py
+++ b/scripts/slave/recipe_modules/skia_swarming/api.py
@@ -161,6 +161,8 @@ class SkiaSwarmingApi(recipe_api.RecipeApi):
       import sys
       with open(sys.argv[1]) as f:
         isolated = json.load(f)
+      if not isolated.get('includes'):
+        isolated['includes'] = []
       for h in sys.argv[2:]:
         isolated['includes'].append(h)
       with open(sys.argv[1], 'w') as f: