Change default computation for ssd dimension.

Macs all have SSDs, so generating ssd:0 for builderless mac builders
forces the definition to also specify ssd=None.

Change-Id: I61b09dab79e9ec37867c6d24c39982f360083a5d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2368322Reviewed-by: Stephen Martinis <martiniss@chromium.org>
Commit-Queue: Garrett Beaty <gbeaty@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801475}

infra/config/lib/builders.star

@@ -144,6 +144,10 @@ xcode_cache = struct(
 
 _DEFAULT_BUILDERLESS_OS_CATEGORIES = [os_category.LINUX]
 
+# Macs all have SSDs, so it doesn't make sense to use the default behavior of
+# setting ssd:0 dimension
+_EXCLUDE_BUILDERLESS_SSD_OS_CATEGORIES = [os_category.MAC]
+
 def _chromium_tests_property(*, bucketed_triggers, project_trigger_overrides):
     chromium_tests = {}
 
@@ -484,7 +488,10 @@ def builder(
 
     ssd = defaults.get_value("ssd", ssd)
     if ssd == args.COMPUTE:
-        ssd = False if builderless else None
+        ssd = None
+        if (builderless and os != None and
+            os.category not in _EXCLUDE_BUILDERLESS_SSD_OS_CATEGORIES):
+            ssd = False
     if ssd != None:
         dimensions["ssd"] = str(int(ssd))
 

infra/config/lib/try.star

@@ -442,7 +442,6 @@ def chromium_swangle_mac_builder(*, name, **kwargs):
     return chromium_swangle_builder(
         name = name,
         cores = None,
-        ssd = None,
         goma_backend = builders.goma.backend.RBE_PROD,
         os = builders.os.MAC_ANY,
         **kwargs

infra/config/subprojects/chromium/master-only/ci.star

@@ -1624,7 +1624,6 @@ ci.fyi_builder(
     os = os.MAC_ANY,
     cpu = cpu.X86_64,
     builderless = True,
-    ssd = None,
     cores = None,
 )
 
@@ -1747,7 +1746,6 @@ ci.fyi_builder(
     os = os.MAC_DEFAULT,
     schedule = "with 3h interval",
     triggered_by = [],
-    ssd = None,
 )
 
 ci.fyi_builder(