Run the webkit layout tests under swarming on linux_chromium_rel_ng.

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 32ddf79c0fc841b2db22486244716854a32e1502..494a12e3c409be7cc446cb8f5c0c0d31760b16c5 100644
--- a/testing/buildbot/chromium.linux.json
+++ b/testing/buildbot/chromium.linux.json
@@ -3373,6 +3373,22 @@
         }
       },
       {
+        "isolate_name": "webkit_layout_tests_exparchive",
+        "name": "webkit_layout_tests_exparchive",
+        "swarming": {
+          "can_use_on_swarming_builders": true,
+          "shards": 16
+        }
+      },
+      {
+        "isolate_name": "some_webkit_layout_tests",
+        "name": "some_webkit_layout_tests",
+        "swarming": {
+          "can_use_on_swarming_builders": true,
+          "shards": 4
+        }
+      },
+      {
         "isolate_name": "telemetry_gpu_unittests",
         "name": "telemetry_gpu_unittests",
         "override_compile_targets": [
@@ -3420,6 +3436,13 @@
       {
         "name": "nacl_integration",
         "script": "nacl_integration.py"
+      },
+      {
+        "args": {
+          "shards": 16
+        },
+        "name": "locally_swarmed_webkit_layout_tests",
+        "script": "run_locally_swarmed_webkit_layout_tests.py"
       }
     ]
   },