Enable skipping tests that aren't impacted by change on win swarming

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

Review URL: https://codereview.chromium.org/457823002

Cr-Commit-Position: refs/heads/master@{#288454}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288454 0039d316-1c4b-4281-b951-d872f2087c98

testing/buildbot/chromium_trybot.json

@@ -217,6 +217,7 @@
   "filter_tests_builders": [
     "linux_chromium_rel_swarming",
     "win_chromium_rel",
+    "win_chromium_rel_swarming",
     "win_chromium_x64_rel"
   ]
 }