win: Include x64 bots in GetPreferredTryMasters

Otherwise, `git cl try` when there's only _win files will not be try'd on x64 bots.

[email protected], [email protected]
BUG=438414,436603

Review URL: https://codereview.chromium.org/769333003

Cr-Commit-Position: refs/heads/master@{#306840}
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 6762e27..e141c6bc 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -1743,9 +1743,10 @@
     ])
   if all(re.search('(^|[/_])win[/_.]', f) for f in files):
     return GetDefaultTryConfigs([
+        'win8_chromium_rel',
         'win_chromium_dbg',
         'win_chromium_rel',
-        'win8_chromium_rel',
+        'win_chromium_x64_rel',
     ])
   if all(re.search(r'(^|[\\\/_])android[\\\/_.]', f) for f in files):
     return GetDefaultTryConfigs([