Support sharding for swarmed isolated script tests.

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

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
       "--master",
       "chromium.linux",
       "--builder",
       "Linux Tests",
@@ skipping 209 matching lines @@
     "name": "read test spec",
     "~followup_annotations": [
       "@@@STEP_TEXT@path: [SLAVE_BUILD]/src/testing/buildbot/chromium.linux.json@@@",
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"Linux Tests\": {@@@",
       "@@@STEP_LOG_LINE@json.output@    \"isolated_scripts\": [@@@",
       "@@@STEP_LOG_LINE@json.output@      {@@@",
       "@@@STEP_LOG_LINE@json.output@        \"isolate_name\": \"telemetry_gpu_unittests\", @@@",
       "@@@STEP_LOG_LINE@json.output@        \"name\": \"telemetry_gpu_unittests\", @@@",
       "@@@STEP_LOG_LINE@json.output@        \"swarming\": {@@@",
-      "@@@STEP_LOG_LINE@json.output@          \"can_use_on_swarming_builders\": true@@@",
+      "@@@STEP_LOG_LINE@json.output@          \"can_use_on_swarming_builders\": true, @@@",
+      "@@@STEP_LOG_LINE@json.output@          \"shards\": 2@@@",
       "@@@STEP_LOG_LINE@json.output@        }@@@",
       "@@@STEP_LOG_LINE@json.output@      }@@@",
       "@@@STEP_LOG_LINE@json.output@    ]@@@",
       "@@@STEP_LOG_LINE@json.output@  }@@@",
       "@@@STEP_LOG_LINE@json.output@}@@@",
       "@@@STEP_LOG_END@json.output@@@"
     ]
   },
   {
     "cmd": [
@@ skipping 75 matching lines @@
       "-u",
       "[SLAVE_BUILD]/src/tools/swarming_client/swarming.py",
       "trigger",
       "--swarming",
       "https://chromium-swarm.appspot.com",
       "--isolate-server",
       "https://isolateserver.appspot.com",
       "--priority",
       "25",
       "--shards",
-      "1",
+      "2",
       "--task-name",
       "telemetry_gpu_unittests/Ubuntu-12.04/eeeeeeeeee/Linux Tests/571",
       "--dump-json",
       "/path/to/tmp/json",
       "--expiration",
       "3600",
       "--io-timeout",
       "1200",
       "--hard-timeout",
       "3600",
@@ skipping 36 matching lines @@
       "--isolated-script-test-output=${ISOLATED_OUTDIR}/output.json"
     ],
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "[trigger] telemetry_gpu_unittests on Ubuntu-12.04",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_task_name\": \"telemetry_gpu_unittests/Ubuntu-12.04/eeeeeeeeee/Linux Tests/571\", @@@",
       "@@@STEP_LOG_LINE@json.output@  \"tasks\": {@@@",
-      "@@@STEP_LOG_LINE@json.output@    \"telemetry_gpu_unittests/Ubuntu-12.04/eeeeeeeeee/Linux Tests/571\": {@@@",
+      "@@@STEP_LOG_LINE@json.output@    \"telemetry_gpu_unittests/Ubuntu-12.04/eeeeeeeeee/Linux Tests/571:2:0\": {@@@",
       "@@@STEP_LOG_LINE@json.output@      \"shard_index\": 0, @@@",
       "@@@STEP_LOG_LINE@json.output@      \"task_id\": \"10000\", @@@",
       "@@@STEP_LOG_LINE@json.output@      \"view_url\": \"https://chromium-swarm.appspot.com/user/task/10000\"@@@",
+      "@@@STEP_LOG_LINE@json.output@    }, @@@",
+      "@@@STEP_LOG_LINE@json.output@    \"telemetry_gpu_unittests/Ubuntu-12.04/eeeeeeeeee/Linux Tests/571:2:1\": {@@@",
+      "@@@STEP_LOG_LINE@json.output@      \"shard_index\": 1, @@@",
+      "@@@STEP_LOG_LINE@json.output@      \"task_id\": \"10100\", @@@",
+      "@@@STEP_LOG_LINE@json.output@      \"view_url\": \"https://chromium-swarm.appspot.com/user/task/10100\"@@@",
       "@@@STEP_LOG_LINE@json.output@    }@@@",
       "@@@STEP_LOG_LINE@json.output@  }@@@",
       "@@@STEP_LOG_LINE@json.output@}@@@",
       "@@@STEP_LOG_END@json.output@@@",
-      "@@@STEP_LINK@shard #0@https://chromium-swarm.appspot.com/user/task/10000@@@"
+      "@@@STEP_LINK@shard #0@https://chromium-swarm.appspot.com/user/task/10000@@@",
+      "@@@STEP_LINK@shard #1@https://chromium-swarm.appspot.com/user/task/10100@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]/src/tools/swarming_client/swarming.py",
       "collect",
       "--swarming",
       "https://chromium-swarm.appspot.com",
       "--decorate",
       "--print-status-updates",
       "--shards",
-      "1",
+      "2",
       "telemetry_gpu_unittests/Ubuntu-12.04/eeeeeeeeee/Linux Tests/571",
       "--task-output-dir",
       "/path/to/tmp/"
     ],
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "telemetry_gpu_unittests on Ubuntu-12.04",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@outdir_json@{@@@",
-      "@@@STEP_LOG_LINE@outdir_json@  \"0/output.json\": \"{\\\"failures\\\": [], \\\"valid\\\": true}\", @@@",
-      "@@@STEP_LOG_LINE@outdir_json@  \"summary.json\": \"{\\\"shards\\\": [{\\\"internal_failure\\\": false, \\\"failure\\\": false}]}\"@@@",
+      "@@@STEP_LOG_LINE@outdir_json@  \"0/output.json\": \"{\\\"successes\\\": [\\\"test1.Test1\\\", \\\"test2.Test2\\\"], \\\"failures\\\": [], \\\"valid\\\": true}\", @@@",
+      "@@@STEP_LOG_LINE@outdir_json@  \"1/output.json\": \"{\\\"successes\\\": [\\\"test3.Test3\\\", \\\"test4.Test4\\\"], \\\"failures\\\": [], \\\"valid\\\": true}\", @@@",
+      "@@@STEP_LOG_LINE@outdir_json@  \"summary.json\": \"{\\\"shards\\\": [{\\\"internal_failure\\\": false, \\\"failure\\\": false}, {\\\"internal_failure\\\": false, \\\"failure\\\": false}]}\"@@@",
       "@@@STEP_LOG_LINE@outdir_json@}@@@",
-      "@@@STEP_LOG_END@outdir_json@@@"
+      "@@@STEP_LOG_END@outdir_json@@@",
+      "@@@STEP_LINK@shard #0@https://chromium-swarm.appspot.com/user/task/10000@@@",
+      "@@@STEP_LINK@shard #1@https://chromium-swarm.appspot.com/user/task/10100@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]