Set up mac-chrome official trybot

This CL sets up mac-chrome official try bot, and one of the use cases
is for PGO auto roller to validate the profiles and warm up GOMA
caches for other official builders.

Bug: 1071576
Change-Id: If5ddd46caeccbb5f793b1768ac9790c117055a0d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2159766
Commit-Queue: Yuke Liao <liaoyuke@chromium.org>
Reviewed-by: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#761172}

infra/config/buckets/try.star

@@ -747,6 +747,10 @@ chrome_internal_verifier(
     builder = 'linux-chromeos-chrome',
 )
 
+chrome_internal_verifier(
+    builder = 'mac-chrome',
+)
+
 chrome_internal_verifier(
     builder = 'win_chrome_official',
 )

infra/config/generated/commit-queue.cfg

@@ -71,6 +71,12 @@ config_groups: <
         owner_whitelist_group: "googlers"
         owner_whitelist_group: "project-chromium-robot-committers"
       >
+      builders: <
+        name: "chrome/try/mac-chrome"
+        includable_only: true
+        owner_whitelist_group: "googlers"
+        owner_whitelist_group: "project-chromium-robot-committers"
+      >
       builders: <
         name: "chrome/try/win64-chrome"
         includable_only: true

tools/mb/mb_config.pyl

@@ -779,6 +779,7 @@
       'chromeos-kevin-compile-chrome': 'chromeos_kevin_include_unwind_tables_official',
       'linux-chrome': 'official_goma',
       'linux-chromeos-chrome': 'official_goma_chromeos_include_unwind_tables',
+      'mac-chrome': 'official_goma',
       'win64-chrome': 'official_goma_x64',
       'win_chrome_official': 'official_goma_x86',
       'win-celab-try-rel': 'official_celab_release_bot',