Enable skipping tests that aren't impacted by change on linux

Specifically linux_chromium_rel_swarming.

BUG=109173
TEST=none
R=jam@chromium.org

Review URL: https://codereview.chromium.org/451473002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@287866 0039d316-1c4b-4281-b951-d872f2087c98

testing/buildbot/chromium_trybot.json

@@ -214,5 +214,9 @@
   ],
 
   "non_filter_builders": [
+  ],
+
+  "filter_tests_builders": [
+    "linux_chromium_rel_swarming"
   ]
 }