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

scripts/slave/recipes/v8.expected/full_client_v8_V8_Win64.json

Index: scripts/slave/recipes/v8.expected/full_client_v8_V8_Win64.json
diff --git a/scripts/slave/recipes/v8.expected/full_client_v8_V8_Win64.json b/scripts/slave/recipes/v8.expected/full_client_v8_V8_Win64.json
index 829593bc169218c413117c4062d2e7627778a644..2fb01c90ce31bb1463386b8753bffa3c69685ac9 100644
--- a/scripts/slave/recipes/v8.expected/full_client_v8_V8_Win64.json
+++ b/scripts/slave/recipes/v8.expected/full_client_v8_V8_Win64.json
@@ -226,7 +226,7 @@
       "--tag",
       "slavename:TestSlavename",
       "--tag",
-      "stepname:Check",
+      "stepname:Check on Windows-7-SP1",
       "--idempotent",
       "[dummy hash for bot_default]",
       "--",
@@ -248,7 +248,7 @@
       "${ISOLATED_OUTDIR}/output.json"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "[trigger] Check",
+    "name": "[trigger] Check on Windows-7-SP1",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_task_name\": \"Check/Windows-7-SP1/[dummy has/V8 Win64/571\", @@@",
@@ -321,7 +321,7 @@
       "--tag",
       "slavename:TestSlavename",
       "--tag",
-      "stepname:SimdJs - all",
+      "stepname:SimdJs - all on Windows-7-SP1",
       "--idempotent",
       "[dummy hash for simdjs]",
       "--",
@@ -344,7 +344,7 @@
       "${ISOLATED_OUTDIR}/output.json"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "[trigger] SimdJs - all",
+    "name": "[trigger] SimdJs - all on Windows-7-SP1",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_task_name\": \"SimdJs - all/Windows-7-SP1/[dummy has/V8 Win64/571\", @@@",
@@ -417,7 +417,7 @@
       "--tag",
       "slavename:TestSlavename",
       "--tag",
-      "stepname:Test262 - no variants",
+      "stepname:Test262 - no variants on Windows-7-SP1",
       "--idempotent",
       "[dummy hash for test262]",
       "--",
@@ -441,7 +441,7 @@
       "${ISOLATED_OUTDIR}/output.json"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "[trigger] Test262 - no variants",
+    "name": "[trigger] Test262 - no variants on Windows-7-SP1",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_task_name\": \"Test262 - no variants/Windows-7-SP1/[dummy has/V8 Win64/571\", @@@",
@@ -514,7 +514,7 @@
       "--tag",
       "slavename:TestSlavename",
       "--tag",
-      "stepname:Mozilla",
+      "stepname:Mozilla on Windows-7-SP1",
       "--idempotent",
       "[dummy hash for mozilla]",
       "--",
@@ -536,7 +536,7 @@
       "${ISOLATED_OUTDIR}/output.json"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "[trigger] Mozilla",
+    "name": "[trigger] Mozilla on Windows-7-SP1",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_task_name\": \"Mozilla/Windows-7-SP1/[dummy has/V8 Win64/571\", @@@",