Enable service_unittests on several bot configurations

testing/buildbot/chromium.mac.json

Index: testing/buildbot/chromium.mac.json
diff --git a/testing/buildbot/chromium.mac.json b/testing/buildbot/chromium.mac.json
index b0d76dbde3fb753de96a33be72591b81322310dc..bab06cb8035a9a6971c746ad1221b6f4bf9d2044 100644
--- a/testing/buildbot/chromium.mac.json
+++ b/testing/buildbot/chromium.mac.json
@@ -297,6 +297,12 @@
         "swarming": {
           "can_use_on_swarming_builders": true
         },
+        "test": "service_unittests"
+      },
+      {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "skia_unittests"
       },
       {
@@ -655,6 +661,12 @@
         "swarming": {
           "can_use_on_swarming_builders": true
         },
+        "test": "service_unittests"
+      },
+      {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "skia_unittests"
       },
       {
@@ -1014,6 +1026,12 @@
         "swarming": {
           "can_use_on_swarming_builders": true
         },
+        "test": "service_unittests"
+      },
+      {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "skia_unittests"
       },
       {
@@ -1361,6 +1379,12 @@
         "swarming": {
           "can_use_on_swarming_builders": true
         },
+        "test": "service_unittests"
+      },
+      {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "skia_unittests"
       },
       {