Fix mac-arm64 test config

The builder is actually in the chromium.mac builder group. Also adds GPU
tests which are useful to be able to run.

Bug: 1106083
Change-Id: I0367ad93e72b52c276fa9f4b5b844625e840d87a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2339935
Commit-Queue: Stephen Martinis <martiniss@chromium.org>
Auto-Submit: Stephen Martinis <martiniss@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Cr-Commit-Position: refs/heads/master@{#795291}

testing/buildbot/waterfalls.pyl

@@ -2326,15 +2326,6 @@
           'isolated_scripts': 'wpt_web_tests',
         },
       },
-      'mac-arm64': {
-        'additional_compile_targets': [
-          'all',
-        ],
-        'test_suites': {
-          'gtest_tests': 'chromium_mac_gtests_no_nacl',
-          'isolated_scripts': 'chromium_mac_rel_isolated_scripts',
-        },
-      },
       'mac-code-coverage': {
         'mixins': [
           'isolate_profile_data',
@@ -4425,6 +4416,19 @@
         'additional_compile_targets': [
           'all',
         ],
+        'os_type': 'mac',
+        'browser_config': 'release',
+        # TODO(thakis): This mixin is almost certainly incorrect. It exists to
+        # make the test suites listed below be valid; this can't be generated
+        # swarming dimensions are set.
+        'mixins': [
+          'mac_mini_intel_gpu_stable',
+        ],
+        'test_suites': {
+          'gtest_tests': 'gpu_fyi_mac_release_gtests',
+          'gpu_telemetry_tests': 'gpu_fyi_mac_release_telemetry_tests',
+          'isolated_scripts': 'rendering_desktop_representative_perf_tests_isolated_scripts',
+        },
       },
     },
   },