Stop branch builders from closing the tree.

Bug: 1094768,1105382
Change-Id: I4adef61ba684a97f729c02e2557736cbf6def33c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2297031
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Auto-Submit: Owen Rodley <orodley@chromium.org>
Cr-Commit-Position: refs/heads/master@{#788441}

infra/config/lib/ci.star

@@ -454,10 +454,15 @@ def ci_builder(
       'chromium-tree-closer' config in notifiers.star for the full criteria.
     notifies - Any extra notifiers to attach to this builder.
   """
+
+  # Branch builders should never close the tree, only builders from the main
+  # "ci" bucket.
+  bucket = defaults.get_value_from_kwargs('bucket', kwargs)
+  if tree_closing and bucket == 'ci':
+    notifies = (notifies or []) + ['chromium-tree-closer', 'chromium-tree-closer-email']
+
   # Define the builder first so that any validation of luci.builder arguments
   # (e.g. bucket) occurs before we try to use it
-  if tree_closing:
-    notifies = (notifies or []) + ['chromium-tree-closer', 'chromium-tree-closer-email']
   ret = builders.builder(
       name = name,
       resultdb_bigquery_exports = [resultdb.export_test_results(
@@ -473,7 +478,6 @@ def ci_builder(
       console_view = defaults.get_value_from_kwargs('mastername', kwargs)
 
     if console_view:
-      bucket = defaults.get_value_from_kwargs('bucket', kwargs)
       add_to_console_view = defaults.get_value(
           'add_to_console_view', add_to_console_view)
 

infra/config/subprojects/chromium/versioned/m85/buckets/ci.star

@@ -230,7 +230,6 @@ ci.chromium_builder(
     # TODO: Change this back down to something reasonable once these builders
     # have populated their cached by getting through the compile step
     execution_timeout = 6 * time.hour,
-    tree_closing = False,
 )
 
 ci.chromium_builder(
@@ -246,7 +245,6 @@ ci.chromium_builder(
     # TODO: Change this back down to something reasonable once these builders
     # have populated their cached by getting through the compile step
     execution_timeout = 10 * time.hour,
-    tree_closing = False,
 )
 
 ci.chromium_builder(
@@ -262,7 +260,6 @@ ci.chromium_builder(
     # TODO: Change this back down to something reasonable once these builders
     # have populated their cached by getting through the compile step
     execution_timeout = 10 * time.hour,
-    tree_closing = False,
 )
 
 ci.chromiumos_builder(