Make _merge_isolated_script_shards robust to harness failures.

scripts/slave/recipe_modules/test_utils/test_api.py

Index: scripts/slave/recipe_modules/test_utils/test_api.py
diff --git a/scripts/slave/recipe_modules/test_utils/test_api.py b/scripts/slave/recipe_modules/test_utils/test_api.py
index f373fefad758c0285f3558245d09139da9aaccea..e83f77bcde154f18be8bdc51a863b6ec3cc1e1a0 100644
--- a/scripts/slave/recipe_modules/test_utils/test_api.py
+++ b/scripts/slave/recipe_modules/test_utils/test_api.py
@@ -115,7 +115,8 @@ class TestUtilsTestApi(recipe_test_api.RecipeTestApi):
   def canned_isolated_script_output(self, passing, is_win, swarming=False,
                                     shards=1, swarming_internal_failure=False,
                                     isolated_script_passing=True, valid=True,
-                                    missing_shards=[]):
+                                    missing_shards=[],
+                                    empty_shards=[]):
     """Produces a test results' compatible json for isolated script tests. """
     per_shard_results = []
     for i in xrange(shards):
@@ -132,6 +133,7 @@ class TestUtilsTestApi(recipe_test_api.RecipeTestApi):
       else:
         jsonish_results['failures'] = tests_run
         jsonish_results['successes'] = []
+      jsonish_results['times'] = {t : 0.1 for t in tests_run}
       per_shard_results.append(jsonish_results)
     if swarming:
       jsonish_shards = []
@@ -141,10 +143,14 @@ class TestUtilsTestApi(recipe_test_api.RecipeTestApi):
           'failure': not passing,
           'internal_failure': swarming_internal_failure
         })
-        if not i in missing_shards:
+        if i not in missing_shards:
           swarming_path = str(i)
           swarming_path += '\\output.json' if is_win else '/output.json'
-          files_dict[swarming_path] = json.dumps(per_shard_results[i])
+          if i not in empty_shards:
+            files_dict[swarming_path] = json.dumps(per_shard_results[i])
+          else:
+            # Simulate a complete harness failure.
+            files_dict[swarming_path] = ''
       jsonish_summary = {'shards': jsonish_shards}
       files_dict['summary.json'] = json.dumps(jsonish_summary)
       return self.m.raw_io.output_dir(files_dict)