Convert mojo_common_unittests to run exclusively on Swarming

testing/buildbot/chromium.linux.json

Index: testing/buildbot/chromium.linux.json
diff --git a/testing/buildbot/chromium.linux.json b/testing/buildbot/chromium.linux.json
index 8ca7aa2a887f7f7bd08a99df3bf573945836ac6e..3710c31d57f78dc092e8ad83abf07dfc013cf5d6 100644
--- a/testing/buildbot/chromium.linux.json
+++ b/testing/buildbot/chromium.linux.json
@@ -16,6 +16,9 @@
         "test": "ipc_mojo_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "mojo_common_unittests"
       },
       {
@@ -677,6 +680,9 @@
         "test": "midi_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "mojo_common_unittests"
       },
       {
@@ -1007,6 +1013,9 @@
         "test": "midi_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "mojo_common_unittests"
       },
       {
@@ -1327,6 +1336,9 @@
         "test": "midi_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "mojo_common_unittests"
       },
       {