Add Windows on Swarm usage for the Chromium CQ.

It took a long time but Windows is now stable enough to be used by the CQ.
Fallbacks are still using non-Swarm jobs as a safety precaution.

Linux was added in r232775.
OSX was added in r234506.

R=phajdan.jr@chromium.org
BUG=

Review URL: https://codereview.chromium.org/105823014

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/commit-queue@241387 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/projects.py b/projects.py
index 6693d27..35a6632 100644
--- a/projects.py
+++ b/projects.py
@@ -416,7 +416,7 @@
     swarm_enabled_builders_and_tests = {
       ('linux_rel', 'linux_swarm_triggered'): swarm_test_map,
       ('mac_rel', 'mac_swarm_triggered'): swarm_test_map,
-      # ('win_rel', 'win_swarm_triggered'): swarm_test_map,
+      ('win_rel', 'win_swarm_triggered'): swarm_test_map,
     }
 
     step_verifiers += [