swarming: always append task's OS dimension to step name

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

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
       "--master",
       "tryserver.chromium.linux",
       "--builder",
       "linux_chromium_rel_ng",
@@ skipping 437 matching lines @@
       "project:chromium",
       "--tag",
       "purpose:CQ",
       "--tag",
       "purpose:pre-commit",
       "--tag",
       "rietveld:https://codereview.chromium.org/12853011/#ps1",
       "--tag",
       "slavename:TestSlavename",
       "--tag",
-      "stepname:gl_tests (with patch)",
+      "stepname:gl_tests (with patch) on Ubuntu-12.04",
       "--idempotent",
       "--user",
       "commit-bot@chromium.org",
       "[dummy hash for gl_tests]",
       "--",
       "--test-launcher-summary-output=${ISOLATED_OUTDIR}/output.json"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "[trigger] gl_tests (with patch)",
+    "name": "[trigger] gl_tests (with patch) on Ubuntu-12.04",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_task_name\": \"gl_tests (with patch)/Ubuntu-12.04/[dummy has/linux_chromium_rel_ng/571\", @@@",
       "@@@STEP_LOG_LINE@json.output@  \"tasks\": {@@@",
       "@@@STEP_LOG_LINE@json.output@    \"gl_tests (with patch)/Ubuntu-12.04/[dummy has/linux_chromium_rel_ng/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@  }@@@",
@@ skipping 18 matching lines @@
       "collect",
       "--swarming",
       "https://chromium-swarm.appspot.com",
       "--decorate",
       "--print-status-updates",
       "--shards",
       "1",
       "gl_tests (with patch)/Ubuntu-12.04/[dummy has/linux_chromium_rel_ng/571"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "gl_tests (with patch)",
+    "name": "gl_tests (with patch) on Ubuntu-12.04",
     "~followup_annotations": [
       "step returned non-zero exit code: 1",
       "@@@STEP_TEXT@<br/>failures:<br/>Test.Two<br/>@@@",
       "@@@STEP_FAILURE@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[build::test_results]/resources/upload_gtest_test_results.py",
       "--input-gtest-json",
       "{\"per_iteration_data\": [{\"Test.One\": [{\"elapsed_time_ms\": 0, \"output_snippet\": \"\", \"status\": \"SUCCESS\"}], \"Test.Three\": [{\"elapsed_time_ms\": 0, \"output_snippet\": \"\", \"status\": \"SUCCESS\"}], \"Test.Two\": [{\"elapsed_time_ms\": 0, \"output_snippet\": \"\", \"status\": \"FAILURE\"}]}]}",
       "--master-name",
       "tryserver.chromium.linux",
       "--builder-name",
       "linux_chromium_rel_ng",
       "--build-number",
       "571",
       "--test-type",
-      "gl_tests (with patch)",
+      "gl_tests (with patch) on Ubuntu-12.04",
       "--test-results-server",
       "test-results.appspot.com",
       "--chrome-revision",
       "170242"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "Upload to test-results [gl_tests (with patch)]"
+    "name": "Upload to test-results [gl_tests (with patch) on Ubuntu-12.04]"
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
       "--master",
       "tryserver.chromium.linux",
       "--builder",
       "linux_chromium_rel_ng",
@@ skipping 246 matching lines @@
       "project:chromium",
       "--tag",
       "purpose:CQ",
       "--tag",
       "purpose:pre-commit",
       "--tag",
       "rietveld:https://codereview.chromium.org/12853011/#ps1",
       "--tag",
       "slavename:TestSlavename",
       "--tag",
-      "stepname:gl_tests (without patch)",
+      "stepname:gl_tests (without patch) on Ubuntu-12.04",
       "--idempotent",
       "--user",
       "commit-bot@chromium.org",
       "[dummy hash for gl_tests]",
       "--",
       "--gtest_filter=Test.Two",
       "--test-launcher-summary-output=${ISOLATED_OUTDIR}/output.json"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "[trigger] gl_tests (without patch)",
+    "name": "[trigger] gl_tests (without patch) on Ubuntu-12.04",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_task_name\": \"gl_tests (without patch)/Ubuntu-12.04/[dummy has/linux_chromium_rel_ng/571\", @@@",
       "@@@STEP_LOG_LINE@json.output@  \"tasks\": {@@@",
       "@@@STEP_LOG_LINE@json.output@    \"gl_tests (without patch)/Ubuntu-12.04/[dummy has/linux_chromium_rel_ng/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@  }@@@",
@@ skipping 18 matching lines @@
       "collect",
       "--swarming",
       "https://chromium-swarm.appspot.com",
       "--decorate",
       "--print-status-updates",
       "--shards",
       "1",
       "gl_tests (without patch)/Ubuntu-12.04/[dummy has/linux_chromium_rel_ng/571"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "gl_tests (without patch)",
+    "name": "gl_tests (without patch) on Ubuntu-12.04",
     "~followup_annotations": [
       "@@@STEP_LINK@shard #0 isolated out@blah@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[build::test_results]/resources/upload_gtest_test_results.py",
       "--input-gtest-json",
       "{\"per_iteration_data\": [{\"Test.One\": [{\"elapsed_time_ms\": 0, \"output_snippet\": \"\", \"status\": \"SUCCESS\"}], \"Test.Three\": [{\"elapsed_time_ms\": 0, \"output_snippet\": \"\", \"status\": \"SUCCESS\"}], \"Test.Two\": [{\"elapsed_time_ms\": 0, \"output_snippet\": \"\", \"status\": \"SUCCESS\"}]}], \"swarming_summary\": {\"shards\": [{\"outputs_ref\": {\"view_url\": \"blah\"}}]}}",
       "--master-name",
       "tryserver.chromium.linux",
       "--builder-name",
       "linux_chromium_rel_ng",
       "--build-number",
       "571",
       "--test-type",
-      "gl_tests (without patch)",
+      "gl_tests (without patch) on Ubuntu-12.04",
       "--test-results-server",
       "test-results.appspot.com",
       "--chrome-revision",
       "170242"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "Upload to test-results [gl_tests (without patch)]"
+    "name": "Upload to test-results [gl_tests (without patch) on Ubuntu-12.04]"
   },
   {
     "cmd": [
       "python",
       "-u",
       "import sys; sys.exit(1)"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "gl_tests (retry summary)",
     "~followup_annotations": [
       "step returned non-zero exit code: 1",
       "@@@STEP_TEXT@<br/>failures:<br/>Test.Two<br/>@@@",
       "@@@STEP_FAILURE@@@",
       "@@@SET_BUILD_PROPERTY@failure_type@\"TEST_FAILURE\"@@@",
       "@@@SET_BUILD_PROPERTY@failure_hash@\"2c817ab2d4394c69c9b8a0698b954936d9e1fb76\"@@@"
     ]
   },
   {
     "name": "$result",
     "reason": "1 out of 1 aggregated steps failed. Failures: Step('gl_tests (retry summary)') failed with return_code 1",
     "status_code": 1
   }
 ]