While landing https://chromium-review.googlesource.com/c/chromium/src/+/917007/4, I noticed that Extensions/ExtensionProtocolsTest.VerificationSeenForFileAccessErrors/0 fails under tsan for that CL. However, that behavior is also reproducible @tott locally [1] when I tried. We need to be protecting ContentVerifyJob's member access with locks properly, it seems that ContnetVerifyJob::content_hash_reader_ access is fundamentally racey @tott (don't know why current bots complain though).

[1]
export TSAN_OPTIONS="external_symbolizer_path=third_party/llvm-build/Release+Asserts/bin/llvm-symbolizer"

I have following gn flags:
is_tsan = true
enable_nacl = false
is_debug = false
use_goma = true

ninja -C out/tsan unit_tests -j 1000 && ./out/tsan/unit_tests --gtest_filter=*ExtensionProtocolsTest.VerificationSeenForFileAccess* --gtest_repeat=5

Snip of data race logs:
 following race:
WARNING: ThreadSanitizer: data race (pid=31342)
  Read of size 8 at 0x7b2400009bf0 by main thread:
    #0 memcpy /b/build/slave/linux_upload_clang/build/src/third_party/llvm/compiler-rt/lib/tsan/../sanitizer_common/sanitizer_common_interceptors.inc:782 (unit_tests+0x22e189d)
    #1 swap<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::__rep> buildtools/third_party/libc++/trunk/include/type_traits:4646 (unit_tests+0x5c05317)
    #2 swap buildtools/third_party/libc++/trunk/include/string:3091 (unit_tests+0x5c05317)
    #3 OnHashesReady extensions/browser/content_verify_job.cc:193 (unit_tests+0x5c05317)
    ... (snip)
    #50 main chrome/test/base/run_all_unittests.cc:30 (unit_tests+0x6f48c2d)

  Previous write of size 8 at 0x7b2400009bf0 by thread T5 (mutexes: write M892973951956187080, write M892411070721858616):
    #0 __set_long_pointer buildtools/third_party/libc++/trunk/include/string:1331 (libc++.so+0xe5f34)
    #1 __grow_by_and_replace buildtools/third_party/libc++/trunk/include/string:1970 (libc++.so+0xe5f34)
    #2 append buildtools/third_party/libc++/trunk/include/string:2223 (libc++.so+0xe5f34)
    #3 BytesRead extensions/browser/content_verify_job.cc:78 (unit_tests+0x5c05742)
    #4 OnBytesRead extensions/browser/extension_protocols.cc:718 (unit_tests+0x5c450ab)
    #5 Start content/browser/file_url_loader_factory.cc:481 (unit_tests+0x5594bf7)
    #6 CreateAndStart content/browser/file_url_loader_factory.cc:311 (unit_tests+0x5594bf7)
    ... (snip)
    #18 ThreadFunc base/threading/platform_thread_posix.cc:75 (unit_tests+0x7cfdaed)

  Location is heap block of size 144 at 0x7b2400009bd0 allocated by main thread:
    #0 operator new(unsigned long) /b/build/slave/linux_upload_clang/build/src/third_party/llvm/compiler-rt/lib/tsan/rtl/tsan_new_delete.cc:57 (unit_tests+0x23405a9)
    #1 CreateJobFor extensions/browser/content_verifier.cc:126 (unit_tests+0x5c00b12)
    #2 StartVerifyJob extensions/browser/extension_protocols.cc:962 (unit_tests+0x5c4472b)
    #3 Invoke<network::ResourceRequest, mojo::InterfaceRequest<network::mojom::URLLoader>, mojo::InterfacePtr<network::mojom::URLLoaderClient>, scoped_refptr<extensions::ContentVerifier>, extensions::ExtensionResource, scoped_refptr<net::HttpResponseHeaders> > base/bind_internal.h:402 (unit_tests+0x5c44a7c)
    ... (snip)
    #37 main chrome/test/base/run_all_unittests.cc:30 (unit_tests+0x6f48c2d)