[pinpoint] Support multiple Swarming tasks.

dashboard/dashboard/pinpoint/models/quest/run_test_test.py

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import unittest
 
 import mock
 
 from dashboard.pinpoint.models.quest import run_test
 
@@ skipping 90 matching lines @@
         'failure': False,
         'outputs_ref': {'isolated': 'output isolate hash'},
         'state': 'COMPLETED',
     }
     execution.Poll()
 
     self.assertTrue(execution.completed)
     self.assertFalse(execution.failed)
     self.assertEqual(execution.result_values, (None,))
     self.assertEqual(execution.result_arguments,
-                     {'isolate_hash': 'output isolate hash'})
+                     {'isolate_hashes': ('output isolate hash',)})
 
     # Start a second Execution to check bot_id handling. We get a bot_id from
     # Swarming from the first Execution and reuse it in subsequent Executions.
     execution = quest.Start('input isolate hash')
     execution.Poll()
 
     self.assertNewTaskHasBotId(swarming_tasks_new)
 
 
 @mock.patch('dashboard.services.swarming_service.Tasks.New')
@@ skipping 92 matching lines @@
         'bot_id': 'bot id',
         'exit_code': 0,
         'failure': False,
         'outputs_ref': {'isolated': 'output isolate hash'},
         'state': 'COMPLETED',
     }
     execution_1.Poll()
     execution_2.Poll()
 
     self.assertEqual(swarming_tasks_new.call_count, 2)