Add linux_chromium_clobber_rel_ng as a 10% experiment.

BUG=453471

Review URL: https://codereview.chromium.org/922293004

Cr-Commit-Position: refs/heads/master@{#317363}

testing/commit_queue/config.json

@@ -8,7 +8,8 @@
                         "cast_shell": ["defaulttests"],
                         "cast_shell_apk": ["defaulttests"],
                         "linux_android_rel_ng": ["defaulttests"],
-                        "linux_chromium_asan_rel_ng": ["defaulttests"]
+                        "linux_chromium_asan_rel_ng": ["defaulttests"],
+                        "linux_chromium_clobber_rel_ng": ["defaulttests"]
                     },
                     "tryserver.chromium.mac": {
                         "mac_chromium_gn_rel": ["defaulttests"]