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

scripts/slave/recipes/v8.expected/full_client_v8_V8_Linux___debug___nosse4.json

Index: scripts/slave/recipes/v8.expected/full_client_v8_V8_Linux___debug___nosse4.json
diff --git a/scripts/slave/recipes/v8.expected/full_client_v8_V8_Linux___debug___nosse4.json b/scripts/slave/recipes/v8.expected/full_client_v8_V8_Linux___debug___nosse4.json
index d4f5fae2f60de52768d53f5e9e207d0b4b946220..0d48ddaf2c235582f4890da597cae53317285f7b 100644
--- a/scripts/slave/recipes/v8.expected/full_client_v8_V8_Linux___debug___nosse4.json
+++ b/scripts/slave/recipes/v8.expected/full_client_v8_V8_Linux___debug___nosse4.json
@@ -151,7 +151,7 @@
       "--tag",
       "slavename:TestSlavename",
       "--tag",
-      "stepname:Check",
+      "stepname:Check on Ubuntu-12.04",
       "--idempotent",
       "[dummy hash for bot_default]",
       "--",
@@ -175,7 +175,7 @@
       "${ISOLATED_OUTDIR}/output.json"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "[trigger] Check",
+    "name": "[trigger] Check on Ubuntu-12.04",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_task_name\": \"Check/Ubuntu-12.04/[dummy has/V8 Linux - debug - nosse4/571\", @@@",
@@ -248,7 +248,7 @@
       "--tag",
       "slavename:TestSlavename",
       "--tag",
-      "stepname:Test262 - no variants",
+      "stepname:Test262 - no variants on Ubuntu-12.04",
       "--idempotent",
       "[dummy hash for test262]",
       "--",
@@ -274,7 +274,7 @@
       "${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 - debug - nosse4/571\", @@@",
@@ -347,7 +347,7 @@
       "--tag",
       "slavename:TestSlavename",
       "--tag",
-      "stepname:Mozilla",
+      "stepname:Mozilla on Ubuntu-12.04",
       "--idempotent",
       "[dummy hash for mozilla]",
       "--",
@@ -371,7 +371,7 @@
       "${ISOLATED_OUTDIR}/output.json"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "[trigger] Mozilla",
+    "name": "[trigger] Mozilla on Ubuntu-12.04",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_task_name\": \"Mozilla/Ubuntu-12.04/[dummy has/V8 Linux - debug - nosse4/571\", @@@",
@@ -444,7 +444,7 @@
       "--tag",
       "slavename:TestSlavename",
       "--tag",
-      "stepname:SimdJs - all",
+      "stepname:SimdJs - all on Ubuntu-12.04",
       "--idempotent",
       "[dummy hash for simdjs]",
       "--",
@@ -469,7 +469,7 @@
       "${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 - debug - nosse4/571\", @@@",