Convert sbox_unittests to run exclusively on Swarming

testing/buildbot/chromium.win.json

Index: testing/buildbot/chromium.win.json
diff --git a/testing/buildbot/chromium.win.json b/testing/buildbot/chromium.win.json
index 3e83247e3634af9a32bdb9665ac25a6ef4a26bc7..40fb0db72535a9f9bbf04f9a9ccf102d445d97a0 100644
--- a/testing/buildbot/chromium.win.json
+++ b/testing/buildbot/chromium.win.json
@@ -223,6 +223,9 @@
         "test": "sbox_integration_tests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "sbox_unittests"
       },
       {
@@ -545,6 +548,9 @@
         "test": "sbox_integration_tests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "sbox_unittests"
       },
       {
@@ -990,6 +996,9 @@
         "test": "sbox_integration_tests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "sbox_unittests"
       },
       {
@@ -1292,6 +1301,9 @@
         "test": "sbox_integration_tests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "sbox_unittests"
       },
       {
@@ -1753,6 +1765,9 @@
         "test": "sbox_integration_tests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "sbox_unittests"
       },
       {