Opt into async tracing in the classes pane tests
Opt into async tracing in the classes pane tests

The tests has been timing out on the CQ.

Bug: chromium:1181777
Change-Id: Iaae1139f913c7f61052dc3bc6249b9596c311368
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2718285
Commit-Queue: Philip Pfaffe <639a645feae3653b7aaefa0387217d375f2f82ff@chromium.org>
Reviewed-by: Alex Rudenko <d8d88e7d7e77f69e23d1d1432231196fb8e02a62@chromium.org>

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