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- Currently empty element
- Will later add the test section of a diagnostics card such as
  button to run tests and a routine-result-list to show results.

Bug: 1125150
Test: browser_tests --gtest_filter=DiagnosticsApp*
Change-Id: I64597f5f89c478f74a7900d46b415948d3c1d27a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2461636
Commit-Queue: Zentaro Kavanagh <zentaro@chromium.org>
Reviewed-by: Bailey Berro <baileyberro@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815662}