Add finch-swarming mixins and move finch tests to its own pool.

Change-Id: Ic14d0b9e86bcfe499bf679d14ee0aa4910a1e732
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3684951
Reviewed-by: Ben Pastene <[email protected]>
Commit-Queue: Hao Wu <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1012290}
diff --git a/testing/buildbot/test_suite_exceptions.pyl b/testing/buildbot/test_suite_exceptions.pyl
index 24ee6408..fb03e6ce 100644
--- a/testing/buildbot/test_suite_exceptions.pyl
+++ b/testing/buildbot/test_suite_exceptions.pyl
@@ -3054,8 +3054,24 @@
   },
   'variations_smoke_tests': {
     'modifications': {
+      'linux-chrome': {
+        'swarming': {
+          'dimension_sets': [
+            {
+              'pool': 'chrome.tests.finch',
+            },
+          ],
+        },
+      },
       'win-chrome': {
         'experiment_percentage': 100,
+        'swarming': {
+          'dimension_sets': [
+            {
+              'pool': 'chrome.tests.finch',
+            },
+          ],
+        },
       },
     },
   },