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

scripts/slave/recipes/v8.expected/full_client_v8_V8_Linux___shared.json

Index: scripts/slave/recipes/v8.expected/full_client_v8_V8_Linux___shared.json
diff --git a/scripts/slave/recipes/v8.expected/full_client_v8_V8_Linux___shared.json b/scripts/slave/recipes/v8.expected/full_client_v8_V8_Linux___shared.json
index a8df038c56bfd5e9ae4ff40b6ce3fb80bf1a1b40..b2ab069a2df878c9605ac6eb9a9b05fc0c225bd3 100644
--- a/scripts/slave/recipes/v8.expected/full_client_v8_V8_Linux___shared.json
+++ b/scripts/slave/recipes/v8.expected/full_client_v8_V8_Linux___shared.json
@@ -235,7 +235,7 @@
       "--tag",
       "slavename:TestSlavename",
       "--tag",
-      "stepname:Check",
+      "stepname:Check on Ubuntu-12.04",
       "--idempotent",
       "[dummy hash for bot_default]",
       "--",
@@ -257,7 +257,7 @@
       "${ISOLATED_OUTDIR}/output.json"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "[trigger] Check",
+    "name": "[trigger] Check on Ubuntu-12.04",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_task_name\": \"Check/Ubuntu-12.04/[dummy has/V8 Linux - shared/571\", @@@",
@@ -330,7 +330,7 @@
       "--tag",
       "slavename:TestSlavename",
       "--tag",
-      "stepname:Test262 - no variants",
+      "stepname:Test262 - no variants on Ubuntu-12.04",
       "--idempotent",
       "[dummy hash for test262]",
       "--",
@@ -354,7 +354,7 @@
       "${ISOLATED_OUTDIR}/output.json"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "[trigger] Test262 - no variants",
+    "name": "[trigger] Test262 - no variants on Ubuntu-12.04",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_task_name\": \"Test262 - no variants/Ubuntu-12.04/[dummy has/V8 Linux - shared/571\", @@@",
@@ -427,7 +427,7 @@
       "--tag",
       "slavename:TestSlavename",
       "--tag",
-      "stepname:Mozilla",
+      "stepname:Mozilla on Ubuntu-12.04",
       "--idempotent",
       "[dummy hash for mozilla]",
       "--",
@@ -449,7 +449,7 @@
       "${ISOLATED_OUTDIR}/output.json"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "[trigger] Mozilla",
+    "name": "[trigger] Mozilla on Ubuntu-12.04",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_task_name\": \"Mozilla/Ubuntu-12.04/[dummy has/V8 Linux - shared/571\", @@@",
@@ -522,7 +522,7 @@
       "--tag",
       "slavename:TestSlavename",
       "--tag",
-      "stepname:SimdJs - all",
+      "stepname:SimdJs - all on Ubuntu-12.04",
       "--idempotent",
       "[dummy hash for simdjs]",
       "--",
@@ -545,7 +545,7 @@
       "${ISOLATED_OUTDIR}/output.json"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "[trigger] SimdJs - all",
+    "name": "[trigger] SimdJs - all on Ubuntu-12.04",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_task_name\": \"SimdJs - all/Ubuntu-12.04/[dummy has/V8 Linux - shared/571\", @@@",