Support swarming dimensions in src-side JSON buildbot files.

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

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "chromium.linux",
       "--builder",
       "Linux Tests",
@@ skipping 117 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@          \"dimension_sets\": [@@@",
+      "@@@STEP_LOG_LINE@json.output@            {@@@",
+      "@@@STEP_LOG_LINE@json.output@              \"gpu\": \"10de:104a\", @@@",
+      "@@@STEP_LOG_LINE@json.output@              \"os\": \"Linux\"@@@",
+      "@@@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_LINE@json.output@  }@@@",
       "@@@STEP_LOG_LINE@json.output@}@@@",
       "@@@STEP_LOG_END@json.output@@@"
     ]
   },
   {
     "cmd": [
@@ skipping 94 matching lines @@
       "trigger",
       "--swarming",
       "https://chromium-swarm.appspot.com",
       "--isolate-server",
       "https://isolateserver.appspot.com",
       "--priority",
       "25",
       "--shards",
       "1",
       "--task-name",
-      "telemetry_gpu_unittests/Ubuntu-12.04/eeeeeeeeee/Linux Tests/571",
+      "telemetry_gpu_unittests on NVIDIA GPU on Linux/Linux/eeeeeeeeee/Linux Tests/571",
       "--dump-json",
       "/path/to/tmp/json",
       "--expiration",
       "3600",
       "--io-timeout",
       "1200",
       "--hard-timeout",
       "3600",
       "--dimension",
       "cpu",
       "x86-64",
       "--dimension",
       "gpu",
-      "none",
+      "10de:104a",
       "--dimension",
       "os",
-      "Ubuntu-12.04",
+      "Linux",
       "--dimension",
       "pool",
       "Chrome",
       "--tag",
       "buildername:Linux Tests",
       "--tag",
       "buildnumber:571",
       "--tag",
       "data:eeeeeeeeeeeeeeeeeeeeeeeeeeeeee",
       "--tag",
       "master:chromium.linux",
       "--tag",
-      "name:telemetry_gpu_unittests",
+      "name:telemetry_gpu_unittests on NVIDIA GPU on Linux",
       "--tag",
-      "os:Ubuntu-12.04",
+      "os:Linux",
       "--tag",
       "project:chromium",
       "--tag",
       "purpose:CI",
       "--tag",
       "purpose:post-commit",
       "--tag",
-      "stepname:telemetry_gpu_unittests",
+      "stepname:telemetry_gpu_unittests on NVIDIA GPU on Linux on Linux",
       "eeeeeeeeeeeeeeeeeeeeeeeeeeeeee",
       "--",
       "--isolated-script-test-output=${ISOLATED_OUTDIR}/output.json"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "[trigger] telemetry_gpu_unittests",
+    "name": "[trigger] telemetry_gpu_unittests on NVIDIA GPU on Linux on Linux",
     "~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@  \"base_task_name\": \"telemetry_gpu_unittests on NVIDIA GPU on Linux/Linux/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 on NVIDIA GPU on Linux/Linux/eeeeeeeeee/Linux Tests/571\": {@@@",
       "@@@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@  }@@@",
       "@@@STEP_LOG_LINE@json.output@}@@@",
       "@@@STEP_LOG_END@json.output@@@",
       "@@@STEP_LINK@shard #0@https://chromium-swarm.appspot.com/user/task/10000@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]/src/tools/swarming_client/swarming.py",
       "collect",
       "--swarming",
       "https://chromium-swarm.appspot.com",
       "--decorate",
       "--print-status-updates",
       "--shards",
       "1",
-      "telemetry_gpu_unittests/Ubuntu-12.04/eeeeeeeeee/Linux Tests/571",
+      "telemetry_gpu_unittests on NVIDIA GPU on Linux/Linux/eeeeeeeeee/Linux Tests/571",
       "--task-output-dir",
       "/path/to/tmp/"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "telemetry_gpu_unittests",
+    "name": "telemetry_gpu_unittests on NVIDIA GPU on Linux on Linux",
     "~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@}@@@",
       "@@@STEP_LOG_END@outdir_json@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]