Add new LayoutNG benchmark to FYI perf bot

Depends on https://chromium-review.googlesource.com/c/chromium/src/+/1185641

Follows the instructions from go/benchmarks-on-fyi-waterfall

This benchmark takes about 12 minutes to run based on my experience with
Pinpoint.

No-Try: True
Change-Id: Ie470b7e6404210275d459378174f1d5aeeb2f518
Reviewed-on: https://chromium-review.googlesource.com/1185642
Commit-Queue: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Ned Nguyen <nednguyen@google.com>
Reviewed-by: Stephen Martinis <martiniss@chromium.org>
Reviewed-by: Chong Zhang <chongz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585535}

testing/buildbot/chromium.perf.fyi.json

@@ -100,6 +100,40 @@
   },
   "Mojo Linux Perf": {
     "isolated_scripts": [
+      {
+        "args": [
+          "--benchmarks=blink_perf.layout_ng",
+          "-v",
+          "--upload-results",
+          "--output-format=histograms",
+          "--browser=release"
+        ],
+        "isolate_name": "performance_test_suite",
+        "merge": {
+          "args": [
+            "--service-account-file",
+            "/creds/service_accounts/service-account-chromium-perf-histograms.json"
+          ],
+          "script": "//tools/perf/process_perf_results.py"
+        },
+        "name": "blink_perf.layout_ng",
+        "override_compile_targets": [
+          "performance_test_suite"
+        ],
+        "swarming": {
+          "can_use_on_swarming_builders": true,
+          "dimension_sets": [
+            {
+              "id": "build186-b7",
+              "pool": "chrome.tests.perf-fyi"
+            }
+          ],
+          "expiration": 36000,
+          "hard_timeout": 14400,
+          "ignore_task_failure": false,
+          "io_timeout": 3600
+        }
+      },
       {
         "args": [
           "--benchmarks=loading.desktop.network_service,rendering.oopd.desktop",