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

linux_chromium_rel_swarming seems find, so I'm trying on windows
next.

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

Review URL: https://codereview.chromium.org/454083003

Cr-Commit-Position: refs/heads/master@{#288425}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288425 0039d316-1c4b-4281-b951-d872f2087c98

testing/buildbot/chromium_trybot.json

@@ -215,6 +215,8 @@
   ],
 
   "filter_tests_builders": [
-    "linux_chromium_rel_swarming"
+    "linux_chromium_rel_swarming",
+    "win_chromium_rel",
+    "win_chromium_x64_rel"
   ]
 }