Remove defunct mac-dummy-rel fake builder

Thus builder existed to allow the mac-rel trybot to mirror something
whose configuration didn't quite match that of the Mac10.13 Tests bot.
That is no longer necessary (we're running webkit_layout_tests on
mac-rel as of crrev.com/c/1793130) so this config can be removed.

This change will not land until we're certain that webkit_layout_tests
in the commit queue is stable.

Bug: 944117
Change-Id: I0c63bd7ca6b83bcb1a91a3b77048a750caf35803
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1776855
Commit-Queue: Aaron Gable <agable@chromium.org>
Reviewed-by: Stephen Martinis <martiniss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697881}

testing/buildbot/generate_buildbot_json.py

@@ -1049,8 +1049,6 @@ class BBJSONGenerator(object):
       'win32-dbg',
       'win-archive-dbg',
       'win32-archive-dbg',
-      # chromium.mac, see https://crbug.com/943804
-      'mac-dummy-rel',
       # Defined in internal configs.
       'chromeos-amd64-generic-google-rel',
       'chromeos-betty-google-rel',

testing/buildbot/test_suite_exceptions.pyl

@@ -128,14 +128,6 @@
           'shards': 20,
         },
       },
-      'mac-dummy-rel': {
-        # A subset of tests seem to cause WindowServer deaths on VMs.
-        # crbug.com/828031 et al.
-        'args': [
-          '--test-launcher-filter-file=../../testing/buildbot/filters/mac_window_server_killers.browser_tests.filter',
-          '--gtest_shuffle',
-        ],
-      },
       'mac-osxbeta-rel': {
         # A subset of tests seem to cause WindowServer deaths on VMs.
         # crbug.com/828031 et al.
@@ -1187,9 +1179,6 @@
       # chromium.linux
       # TODO(dpranke): Should we be running this step on Linux Tests (dbg)(1)?
       'Linux Tests (dbg)(1)',
-
-      # chromium.mac. TODO(https://crbug.com/944117): Remove this.
-      'mac-dummy-rel',
     ],
     'modifications': {
       'Linux Tests': {
@@ -1738,9 +1727,6 @@
       # chromium.win
       'Win 7 Tests x64 (1)',  # 64-bit win is unsupported by the layout tests.
       'Win10 Tests x64 (dbg)',
-
-      # chromium.mac. TODO(https://crbug.com/944117): Remove this.
-      'mac-dummy-rel',
     ],
     'modifications': {
       # chromium.fyi

testing/buildbot/waterfalls.pyl

@@ -3671,18 +3671,6 @@
           ],
         },
       },
-      # This builder doesn't run anywhere. It exists to let mac-rel mirror a bot.
-      'mac-dummy-rel': {
-        'mixins': [
-            'mac_10.13',
-            'no_gpu',
-        ],
-        'test_suites': {
-          'gtest_tests': 'chromium_mac_gtests',
-          'isolated_scripts': 'chromium_mac_rel_isolated_scripts',
-          'scripts': 'chromium_mac_scripts',
-        },
-      },
       'mac-jumbo-rel': {
         'additional_compile_targets': [
           'all'