Explicitly wait for expected number of files in e2e test
Explicitly wait for expected number of files in e2e test

Bug: chromium:1081150
Change-Id: I256df30243ddeea77c4d7c98209e996eb0638dfc
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2193959
Reviewed-by: Philip Pfaffe <639a645feae3653b7aaefa0387217d375f2f82ff@chromium.org>
Commit-Queue: Kim-Anh Tran <a72f38a79b5fac6811022b8a7fb84830d856c9c9@chromium.org>

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