This failure started pretty recently - in https://ci.chromium.org/buildbot/chromium.memory/Linux%20Chromium%20OS%20ASan%20LSan%20Tests%20%281%29/27475

I can repro some LSAN leak reports locally:
    $ cat out/lsan/args.gn 
    is_asan = true
    is_lsan = true
    is_debug = false  # Release build.
    enable_nacl = false
    use_goma = true

    $ ninja -C out/lsan -j 500 -l 25 gin_unittests
    ...

    $ ASAN_OPTIONS="detect_leaks=1 symbolize=1 external_symbolizer_path=$SRC/third_party/llvm-build/Release+Asserts/bin/llvm-symbolizer" out/lsan/gin_unittests --gtest_filter=*ArgumentsTest.TestGetAll*

But... the surprising issue that prevents me from bisecting is that I can also locally repro LSAN leaks going back for quite a while - e.g. at 9b7a2e09ec0532063b6cc14d4e4656898c6decb1 (green build https://ci.chromium.org/buildbot/chromium.memory/Linux%20Chromium%20OS%20ASan%20LSan%20Tests%20%281%29/27471) or 9b7a2e09ec0532063b6cc14d4e4656898c6decb1~2048