Run two more layoutng benchmarks on linux-perf-fyi

Added in https://crrev.com/c/1259122 and https://crrev.com/c/1259125

Change-Id: I7122d66620dd04ba3f14036177a180bd4a26315d
Reviewed-on: https://chromium-review.googlesource.com/1259162Reviewed-by: Ned Nguyen <nednguyen@google.com>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Reviewed-by: Chong Zhang <chongz@chromium.org>
Commit-Queue: Christian Biesinger <cbiesinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#596283}

testing/buildbot/chromium.perf.fyi.json

@@ -294,7 +294,7 @@
     "isolated_scripts": [
       {
         "args": [
-          "--benchmarks=blink_perf.layout_ng",
+          "--benchmarks=blink_perf.layout_ng,blink_perf.paint_layout_ng,loading.desktop_layout_ng",
           "-v",
           "--upload-results",
           "--output-format=histograms",