Turn off swarming for WebKit Mac10.12.

testing/buildbot/chromium.webkit.json

Index: testing/buildbot/chromium.webkit.json
diff --git a/testing/buildbot/chromium.webkit.json b/testing/buildbot/chromium.webkit.json
index d181eaa2d4376299a45536045010bf70a99302ea..fd0f827ef3b3b96ae629bab143fdcb75eeff4aee 100644
--- a/testing/buildbot/chromium.webkit.json
+++ b/testing/buildbot/chromium.webkit.json
@@ -220,27 +220,15 @@
   "WebKit Mac10.12": {
     "gtest_tests": [
       {
-        "swarming": {
-          "can_use_on_swarming_builders": true
-        },
         "test": "blink_heap_unittests"
       },
       {
-        "swarming": {
-          "can_use_on_swarming_builders": true
-        },
         "test": "blink_platform_unittests"
       },
       {
-        "swarming": {
-          "can_use_on_swarming_builders": true
-        },
         "test": "webkit_unit_tests"
       },
       {
-        "swarming": {
-          "can_use_on_swarming_builders": true
-        },
         "test": "wtf_unittests"
       }
     ],