Reland "Run browser_tests as a 25% experiment on Mac10.13 Tests & mac_chromium_rel_ng."

This reverts commit b41baee6f6fc2f2c68c50d0b222f77d4ca20df7e.

Reason for revert: we believe browser_tests are now stable

Original change's description:
> Revert "Run browser_tests as a 25% experiment on Mac10.13 Tests & mac_chromium_rel_ng."
> 
> This reverts commit b20ba21cddf5bd37aeaf36e4056cb019ea912635.
> 
> Reason for revert: Added capacity isn't finding bot deaths as fast as manual, targeted swarming invocations. Will reland this after having some confidence that the 10.13 bot-killer tests are identified.
> 
> Original change's description:
> > Run browser_tests as a 25% experiment on Mac10.13 Tests & mac_chromium_rel_ng.
> > 
> > Bug: 828031
> > Change-Id: I1d4bdb235ad9d93df0653215c7c5928c471b6c16
> > Reviewed-on: https://chromium-review.googlesource.com/c/1277693
> > Reviewed-by: Robert Sesek <[email protected]>
> > Commit-Queue: John Budorick <[email protected]>
> > Cr-Commit-Position: refs/heads/master@{#599364}
> 
> [email protected],[email protected]
> 
> # Not skipping CQ checks because original CL landed > 1 day ago.
> 
> Bug: 828031
> Change-Id: I38c447f53d533eeff40abfd462c3bb1f09eac75f
> Reviewed-on: https://chromium-review.googlesource.com/c/1282283
> Reviewed-by: Robert Sesek <[email protected]>
> Reviewed-by: John Budorick <[email protected]>
> Commit-Queue: Robert Sesek <[email protected]>
> Cr-Commit-Position: refs/heads/master@{#599869}

[email protected],[email protected]

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 828031
Change-Id: I297bdbf59e21ebf50aad80f97f7d3aad83e4ccb7
Reviewed-on: https://chromium-review.googlesource.com/c/1287311
Commit-Queue: Robert Sesek <[email protected]>
Reviewed-by: Robert Sesek <[email protected]>
Reviewed-by: John Budorick <[email protected]>
Cr-Commit-Position: refs/heads/master@{#600841}
diff --git a/testing/buildbot/test_suite_exceptions.pyl b/testing/buildbot/test_suite_exceptions.pyl
index 69589a4..ec423e84 100644
--- a/testing/buildbot/test_suite_exceptions.pyl
+++ b/testing/buildbot/test_suite_exceptions.pyl
@@ -75,7 +75,6 @@
       'mac-views-rel', # https://crbug.com/828031
       # chromium.mac
       'Mac10.10 Tests', # https://crbug.com/828031
-      'Mac10.13 Tests', # https://crbug.com/828031
       # chromium.memory
       'Linux TSan Tests',  # https://crbug.com/368525
       'Mac ASan 64 Tests (1)', # https://crbug.com/828031
@@ -133,6 +132,23 @@
           ],
         },
       },
+      'Mac10.13 Tests': {
+        # 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',
+        ],
+        'experiment_percentage': 25,
+        'swarming': {
+          'dimension_sets': [
+            {
+              'pool': 'Chrome-quarantine',
+              'gpu': 'none',
+            },
+          ],
+        },
+      },
       'Mac10.13 Tests (dbg)': {
         # A subset of tests seem to cause WindowServer deaths on VMs.
         # crbug.com/828031 et al.