Use different core amounts for android CQ builders on branches.

The cores for the android CQ builders were recently doubled because they
were long poles and it significantly improved the build execution time.
However, on the branches where the machines are builderless, there are
not currently builderlss machines with the doubled core count. This will
use the old value for the branches to get CQ runs unblocked.

(cherry picked from commit cd2034ee10fc3062749172582f6d57df6710b7ab)

Change-Id: I904056c92b8b7be8ccfdfacdc31d052b21c553df
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2638094
Commit-Queue: Garrett Beaty <gbeaty@chromium.org>
Auto-Submit: Garrett Beaty <gbeaty@chromium.org>
Reviewed-by: Ben Pastene <bpastene@chromium.org>
Cr-Original-Commit-Position: refs/branch-heads/4389@{#10}
Cr-Original-Branched-From: 9251c5db-refs/heads/master@{#843830}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2638443
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#844932}

infra/config/subprojects/chromium/try.star

@@ -345,7 +345,7 @@ try_.chromium_android_builder(
     name = "android-lollipop-arm-rel",
     branch_selector = branches.STANDARD_MILESTONE,
     builderless = not settings.is_master,
-    cores = 16,
+    cores = branches.value(for_main = 16, for_branches = 8),
     goma_jobs = goma.jobs.J150,
     main_list_view = "try",
     tryjob = try_.job(),
@@ -355,7 +355,7 @@ try_.chromium_android_builder(
     name = "android-marshmallow-arm64-rel",
     branch_selector = branches.STANDARD_MILESTONE,
     builderless = not settings.is_master,
-    cores = 32,
+    cores = branches.value(for_main = 32, for_branches = 16),
     goma_jobs = goma.jobs.J300,
     main_list_view = "try",
     ssd = True,