Convert nacl_loader_unittests to run exclusively on Swarming

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 8000df44c1b6a6b479830456aa4f67e9f2b9b23a..90b204e178356b65ab1b6345e2c168ad68300ceb 100644
--- a/testing/buildbot/chromium.mac.json
+++ b/testing/buildbot/chromium.mac.json
@@ -183,6 +183,9 @@
         "test": "mojo_public_utility_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "nacl_loader_unittests"
       },
       {
@@ -415,6 +418,9 @@
         "test": "mojo_system_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "nacl_loader_unittests"
       },
       {
@@ -659,6 +665,9 @@
         "test": "mojo_system_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "nacl_loader_unittests"
       },
       {
@@ -903,6 +912,9 @@
         "test": "mojo_system_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "nacl_loader_unittests"
       },
       {
@@ -1148,6 +1160,9 @@
         "test": "mojo_system_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "nacl_loader_unittests"
       },
       {