Update isolate files for content tests and enable swarming for them.

testing/buildbot/chromium_trybot.json

Index: testing/buildbot/chromium_trybot.json
diff --git a/testing/buildbot/chromium_trybot.json b/testing/buildbot/chromium_trybot.json
index f319fbfb37b1e6c57256b826e4c0a35a9ba44b77..b3e38275cc1c568d8c1a87faf8f3787c969ab056 100644
--- a/testing/buildbot/chromium_trybot.json
+++ b/testing/buildbot/chromium_trybot.json
@@ -40,8 +40,18 @@
       "test": "courgette_unittests",
       "platforms": ["win"]
     },
-    "content_browsertests",
-    "content_unittests",
+    {
+      "test": "content_browsertests",
+      "swarming": {
+        "can_use_on_swarming_builders": true
+      }
+    },
+    {
+      "test": "content_unittests",
+      "swarming": {
+        "can_use_on_swarming_builders": true
+      }
+    },
     "crypto_unittests",
     {
       "test": "dbus_unittests",