Updating swarming api to check for chartjson results from a finished

scripts/slave/recipes/chromium_trybot.expected/dynamic_isolated_script_test_with_args_on_trybot.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "\nimport sys, os\npath = sys.argv[1]\nmode = int(sys.argv[2])\nif not os.path.isdir(path):\n  if os.path.exists(path):\n    print \"%s exists but is not a dir\" % path\n    sys.exit(1)\n  os.makedirs(path, mode)\n",
       "[BUILDER_CACHE]/linux",
       "511"
     ],
     "name": "makedirs checkout path",
@@ skipping 555 matching lines @@
       "--tag",
       "stepname:telemetry_gpu_unittests (with patch) on Ubuntu-12.04",
       "--user",
       "commit-bot@chromium.org",
       "[dummy hash for telemetry_gpu_unittests]",
       "--",
       "--correct-common-arg",
       "--these-args-should-be-present",
       "--test-machine-name=\"linux_chromium_rel_ng\"",
       "--build-revision=\"f27fede2220bcd326aee3e86ddfd4ebd0fe58cb9\"",
-      "--isolated-script-test-output=${ISOLATED_OUTDIR}/output.json"
+      "--isolated-script-test-output=${ISOLATED_OUTDIR}/output.json",
+      "--isolated-script-test-chartjson-output=${ISOLATED_OUTDIR}/chartjson-output.json"
     ],
     "cwd": "[BUILDER_CACHE]/linux",
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "[trigger] telemetry_gpu_unittests (with patch) on Ubuntu-12.04",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_task_name\": \"telemetry_gpu_unittests (with patch)/Ubuntu-12.04/[dummy has/linux_chromium_rel_ng/571\", @@@",
       "@@@STEP_LOG_LINE@json.output@  \"tasks\": {@@@",
@@ skipping 36 matching lines @@
       "@@@STEP_LOG_END@outdir_json@@@",
       "@@@STEP_LINK@shard #0@https://chromium-swarm.appspot.com/user/task/10000@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]