Convert aura_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 d32c10d3a4077d431698fa8d54cd522cbfd4acda..26fcc1b271fe6201b62ee716ca6750541f9081d8 100644
--- a/testing/buildbot/chromium.win.json
+++ b/testing/buildbot/chromium.win.json
@@ -11,6 +11,9 @@
         "test": "app_shell_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "aura_unittests"
       },
       {
@@ -255,6 +258,9 @@
         "test": "ash_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "aura_unittests"
       },
       {
@@ -636,6 +642,9 @@
         "test": "ash_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "aura_unittests"
       },
       {
@@ -905,6 +914,9 @@
         "test": "ash_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "aura_unittests"
       },
       {
@@ -1303,6 +1315,9 @@
         "test": "app_shell_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "aura_unittests"
       },
       {