Empty per_page_values shouldn't imply test success

scripts/slave/recipe_modules/test_utils/test_api.py

 import json
 
 from recipe_engine import recipe_test_api
 
 from .util import GTestResults, TestResults
 
 class TestUtilsTestApi(recipe_test_api.RecipeTestApi):
   @recipe_test_api.placeholder_step_data
   def test_results(self, test_results, retcode=None):
     return self.m.json.output(test_results.as_jsonish(), retcode)
@@ skipping 94 matching lines @@
 
     retcode = None if passing else 1
     return self.raw_gtest_output(canned_jsonish, retcode)
 
   def raw_gtest_output(self, jsonish, retcode):
     t = GTestResults(jsonish)
     ret = self.gtest_results(t)
     ret.retcode = retcode
     return ret
 
-  def canned_telemetry_gpu_output(self, passing, is_win, swarming=False):
+  def canned_telemetry_gpu_output(self, passing, is_win, swarming=False,
+                                  empty_per_page_values=False):
     """Produces a 'json test results' compatible object for telemetry tests."""
-    jsonish_results = {
-      'per_page_values': [{'type': 'success' if passing else 'failure',
-                           'page_id': 0},
-                          {'type': 'success',
-                           'page_id': 1}],
-      'pages': {'0': {'name': 'Test.Test1'},
-                '1': {'name': 'Test.Test2'}},
-    }
+    if empty_per_page_values:
+      jsonish_results = {
+          'per_page_values': [],
+          'pages': { },
+      }
+    else:
+      jsonish_results = {
+        'per_page_values': [{'type': 'success' if passing else 'failure',
+                             'page_id': 0},
+                            {'type': 'success',
+                             'page_id': 1}],
+        'pages': {'0': {'name': 'Test.Test1'},
+                  '1': {'name': 'Test.Test2'}},
+      }
 
     jsonish_summary = {
       'shards': [
         {
           'failure': not passing,
           'internal_failure': False
         }
       ]
     }
 
     swarming_path = '0\\results.json' if is_win else '0/results.json'
     results_path = swarming_path if swarming else 'results.json'
     files_dict = {
       results_path: json.dumps(jsonish_results),
       'summary.json': json.dumps(jsonish_summary)
     }
     return self.m.raw_io.output_dir(files_dict)