Convert ppapi_unittests to run exclusively on Swarming

testing/buildbot/chromium.chromiumos.json

Index: testing/buildbot/chromium.chromiumos.json
diff --git a/testing/buildbot/chromium.chromiumos.json b/testing/buildbot/chromium.chromiumos.json
index 116f251155958cb73c50962ce9c3fc3ea3378a19..2cfe693029d896db190e9da7bad94561399c01fb 100644
--- a/testing/buildbot/chromium.chromiumos.json
+++ b/testing/buildbot/chromium.chromiumos.json
@@ -222,6 +222,9 @@
         "test": "ozone_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "ppapi_unittests"
       },
       {
@@ -515,6 +518,9 @@
         "test": "net_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "ppapi_unittests"
       },
       {
@@ -807,6 +813,9 @@
         "test": "net_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "ppapi_unittests"
       },
       {