Update masters after the tryserver split.

ui/events/PRESUBMIT.py

Index: ui/events/PRESUBMIT.py
diff --git a/ui/events/PRESUBMIT.py b/ui/events/PRESUBMIT.py
index dcdf2d5fbfdbe5315423bd7423e0c35b76d52060..b6284624e166d7efcadefd97d132fed736a7ea59 100644
--- a/ui/events/PRESUBMIT.py
+++ b/ui/events/PRESUBMIT.py
@@ -16,10 +16,12 @@ def GetPreferredTryMasters(project, change):
                'views_unittests'])
 
   return {
-    'tryserver.chromium': {
-      'linux_chromium_rel': tests,
+    'tryserver.chromium.linux': {
+      'linux_chromium_rel_swarming': tests,
       'linux_chromium_chromeos_rel': tests,
       'linux_chromeos_asan': tests,
+    },
+    'tryserver.chromium.win': {
       'win_chromium_compile_dbg': tests,
       'win_chromium_rel': tests,
     }