Relanding updates to swarming api to add chartjson output.

scripts/slave/recipes/chromium.expected/dynamic_swarmed_isolated_script_test_mac_gpu.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
       "--spec",
       "cache_dir = '[GIT_CACHE]'\nsolutions = [{'deps_file': '.DEPS.git', 'managed': True, 'name': 'src', 'url': 'https://chromium.googlesource.com/chromium/src.git'}]",
       "--patch_root",
       "src",
@@ skipping 369 matching lines @@
       "--tag",
       "purpose:CI",
       "--tag",
       "purpose:post-commit",
       "--tag",
       "slavename:TestSlavename",
       "--tag",
       "stepname:telemetry_gpu_unittests on Intel GPU on Mac on Mac-10.10",
       "eeeeeeeeeeeeeeeeeeeeeeeeeeeeee",
       "--",
-      "--isolated-script-test-output=${ISOLATED_OUTDIR}/output.json"
+      "--isolated-script-test-output=${ISOLATED_OUTDIR}/output.json",
+      "--isolated-script-test-chartjson-output=${ISOLATED_OUTDIR}/chartjson-output.json"
     ],
     "env": {
       "FORCE_MAC_TOOLCHAIN": "1",
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "[trigger] telemetry_gpu_unittests on Intel GPU on Mac on Mac-10.10",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_task_name\": \"telemetry_gpu_unittests on Intel GPU on Mac/Mac-10.10/eeeeeeeeee/Mac10.9 Tests/571\", @@@",
       "@@@STEP_LOG_LINE@json.output@  \"tasks\": {@@@",
@@ skipping 64 matching lines @@
       "--tag",
       "purpose:CI",
       "--tag",
       "purpose:post-commit",
       "--tag",
       "slavename:TestSlavename",
       "--tag",
       "stepname:telemetry_gpu_unittests on NVIDIA GPU on Mac Retina on Mac-10.9",
       "eeeeeeeeeeeeeeeeeeeeeeeeeeeeee",
       "--",
-      "--isolated-script-test-output=${ISOLATED_OUTDIR}/output.json"
+      "--isolated-script-test-output=${ISOLATED_OUTDIR}/output.json",
+      "--isolated-script-test-chartjson-output=${ISOLATED_OUTDIR}/chartjson-output.json"
     ],
     "env": {
       "FORCE_MAC_TOOLCHAIN": "1",
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "[trigger] telemetry_gpu_unittests on NVIDIA GPU on Mac Retina on Mac-10.9",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_task_name\": \"telemetry_gpu_unittests on NVIDIA GPU on Mac Retina/Mac-10.9/eeeeeeeeee/Mac10.9 Tests/571\", @@@",
       "@@@STEP_LOG_LINE@json.output@  \"tasks\": {@@@",
@@ skipping 65 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
   }
 ]