Reland of Size limit gtest collect

scripts/slave/recipe_modules/swarming/resources/collect_gtest_task.py

Index: scripts/slave/recipe_modules/swarming/resources/collect_gtest_task.py
diff --git a/scripts/slave/recipe_modules/swarming/resources/collect_gtest_task.py b/scripts/slave/recipe_modules/swarming/resources/collect_gtest_task.py
index cd82d3b1955c1a3f7debfabf33d5ee75ff4ca6de..76c1db6c3de51765074c821e960a5a93bedbd393 100755
--- a/scripts/slave/recipe_modules/swarming/resources/collect_gtest_task.py
+++ b/scripts/slave/recipe_modules/swarming/resources/collect_gtest_task.py
@@ -95,11 +95,19 @@ def merge_shard_results(output_dir):
   return merged
 
 
+# 100 MB
+OUTPUT_JSON_SIZE_LIMIT = 100 * 1024 * 1024
+
+
 def load_shard_json(output_dir, index):
   """Reads JSON output of a single shard."""
   # 'output.json' is set in swarming/api.py, gtest_task method.
   path = os.path.join(output_dir, str(index), 'output.json')
   try:
+    filesize = os.stat(path).st_size
+    if filesize > OUTPUT_JSON_SIZE_LIMIT:

[Vadim Sh., 2016/09/27 00:10:56]

please log this to stderr

+      raise ValueError()
+
     with open(path) as f:
       return json.load(f)
   except (IOError, ValueError):

[Vadim Sh., 2016/09/27 00:10:56]

catch OSError here, since os.stat can raise it now if 'path' is missing