Require kvm for browser tests

Crostini tests were failing on E2 machines because there was no KVM available.
This CL requires that browser tests are run on machines that have a KVM.

Bug: 1058924
Change-Id: I9178dd5c8fb8e704e853c75c58cf5d0899c4c593
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2088408
Commit-Queue: Stephanie Kim <[email protected]>
Reviewed-by: Aaron Gable <[email protected]>
Cr-Commit-Position: refs/heads/master@{#747454}
diff --git a/testing/buildbot/test_suite_exceptions.pyl b/testing/buildbot/test_suite_exceptions.pyl
index 21e6872..205fb51d 100644
--- a/testing/buildbot/test_suite_exceptions.pyl
+++ b/testing/buildbot/test_suite_exceptions.pyl
@@ -522,6 +522,11 @@
       'linux-chromeos-rel': {
         'swarming': {
           'shards': 20,
+          'dimension_sets': [
+            {
+              'kvm': '1',
+            },
+          ],
         },
       },
       'linux-code-coverage': {