Convert ppapi_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 edc9c06048472c54154e2a935948b88ce53fb651..b01e0a7a628692c1dad065bdaf408dc4c1a77f92 100644
--- a/testing/buildbot/chromium.mac.json
+++ b/testing/buildbot/chromium.mac.json
@@ -271,6 +271,9 @@
         "test": "net_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "ppapi_unittests"
       },
       {
@@ -596,6 +599,9 @@
         "test": "net_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "ppapi_unittests"
       },
       {
@@ -921,6 +927,9 @@
         "test": "net_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "ppapi_unittests"
       },
       {
@@ -1252,6 +1261,9 @@
         "test": "net_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "ppapi_unittests"
       },
       {
@@ -1577,6 +1589,9 @@
         "test": "net_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "ppapi_unittests"
       },
       {
@@ -1903,6 +1918,9 @@
         "test": "net_unittests"
       },
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "ppapi_unittests"
       },
       {