tip / Linux x86-64

1. Build unit_tests with ubsan:

$ gn gen out/ubsan '--args=is_debug=false is_ubsan_no_recover=true is_ubsan=true is_ubsan_vptr=true is_ubsan_null=true symbol_level=2' --check
$ ninja -C out/ubsan unit_tests

2. Run the test:

$ ./out/ubsan/unit_tests --gtest_filter=ChromeContentBrowserClientClearSiteDataTest.RegistrableDomains
IMPORTANT DEBUGGING NOTE: batches of tests are run inside their
own process. For debugging a test inside a debugger, use the
--gtest_filter=<your_test_name> flag along with
--single-process-tests.
Using sharding settings from environment. This is shard 0/1
Using 1 parallel jobs.
Note: Google Test filter = ChromeContentBrowserClientClearSiteDataTest.RegistrableDomains
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from ChromeContentBrowserClientClearSiteDataTest
[ RUN      ] ChromeContentBrowserClientClearSiteDataTest.RegistrableDomains
../../chrome/browser/browsing_data/browsing_data_remover_factory.cc:49:10: runtime error: downcast of address 0x2ec9eb362e00 which does not point to an object of type 'BrowsingDataRemoverImpl'
0x2ec9eb362e00: note: object is of type 'MockBrowsingDataRemover'
 c9 2e 00 00  28 71 b6 12 00 00 00 00  b0 71 b6 12 00 00 00 00  10 2e 36 eb c9 2e 00 00  10 2e 36 eb
              ^~~~~~~~~~~~~~~~~~~~~~~
              vptr for 'MockBrowsingDataRemover'
    #0 0x615b9b9 in BrowsingDataRemoverFactory::GetForBrowserContext(content::BrowserContext*) chrome/browser/browsing_data/browsing_data_remover_factory.cc:49:10
    #1 0x7dfc80 in (anonymous namespace)::ChromeContentBrowserClientClearSiteDataTest::remover() chrome/browser/chrome_content_browser_client_unittest.cc:358:9
    #2 0x7e03d9 in (anonymous namespace)::ChromeContentBrowserClientClearSiteDataTest_RegistrableDomains_Test::TestBody() chrome/browser/chrome_content_browser_client_unittest.cc:506:5
    #3 0x5646981 in testing::Test::Run() testing/gtest/src/gtest.cc:2474:5
    #4 0x5647de3 in testing::TestInfo::Run() testing/gtest/src/gtest.cc:2656:11
    #5 0x56490ed in testing::TestCase::Run() testing/gtest/src/gtest.cc:2774:28
    #6 0x56550f1 in testing::internal::UnitTestImpl::RunAllTests() testing/gtest/src/gtest.cc:4647:43
    #7 0x565408b in testing::UnitTest::Run() testing/gtest/src/gtest.cc:4255:10
    #8 0x47aa840 in RUN_ALL_TESTS testing/gtest/include/gtest/gtest.h:2237:46
    #9 0x47aa840 in base::TestSuite::Run() base/test/test_suite.cc:271
    #10 0x47ad3b4 in Run base/callback.h:85:12
    #11 0x47ad3b4 in base::(anonymous namespace)::LaunchUnitTestsInternal(base::Callback<int (), (base::internal::CopyMode)1, (base::internal::RepeatMode)1> const&, int, int, bool, base::Callback<void (), (base::internal::CopyMode)1, (base::internal::RepeatMode)1> const&) base/test/launcher/unit_test_launcher.cc:211
    #12 0x47ad237 in base::LaunchUnitTests(int, char**, base::Callback<int (), (base::internal::CopyMode)1, (base::internal::RepeatMode)1> const&) base/test/launcher/unit_test_launcher.cc:453:10
    #13 0x479ef4e in main chrome/test/base/run_all_unittests.cc:30:10
    #14 0x7fce5e8bdf44 in __libc_start_main /build/eglibc-oGUzwX/eglibc-2.19/csu/libc-start.c:287
    #15 0x676b20 in _start (/usr/local/google/home/krasin/chr33/src/out/ubsan/unit_tests+0x676b20)

That breakes UBSan Vptr buildbot:
https://build.chromium.org/p/chromium.fyi/builders/UBSanVptr%20Linux/builds/2161