Try to fix blink_perf.layout_ng config

The test failed with a NO_RESOURCE error; try to match the bot config
of the other testsuite exactly.

https://ci.chromium.org/buildbot/chromium.perf.fyi/Mojo%20Linux%20Perf/6935

R=nednguyen@google.com

No-Try: True
Change-Id: I30a90a5991030f26ff70bbedc26fd5c8785fcd33
Reviewed-on: https://chromium-review.googlesource.com/1187074Reviewed-by: Ned Nguyen <nednguyen@google.com>
Commit-Queue: Christian Biesinger <cbiesinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585577}

testing/buildbot/chromium.perf.fyi.json

@@ -124,6 +124,7 @@
           "can_use_on_swarming_builders": true,
           "dimension_sets": [
             {
+              "gpu": "10de:1cb3",
               "id": "build186-b7",
               "pool": "chrome.tests.perf-fyi"
             }