Lots of tests fail flakily.
When they fail, the fail a CHECK in child_port_handshake.cc

Example:
[ RUN      ] WebNavigationApiTest.Api
[0508/050441.815676:ERROR:mach_extensions.cc(68)] bootstrap_check_in org.chromium.crashpad.child_port_handshake.63986.1016711.XZZHRGNRQLPFUUCU: unknown error code (141)
[0508/050441.815796:FATAL:child_port_handshake.cc(111)] Check failed: server_port.is_valid().
0   crashpad_handler                    0x00000001040df6ac base::debug::StackTrace::StackTrace(unsigned long) + 28
1   crashpad_handler                    0x00000001040cc94f logging::LogMessage::~LogMessage() + 223
2   crashpad_handler                    0x00000001040e9374 crashpad::ChildPortHandshake::RunServerForFD(base::ScopedGeneric<int, base::internal::ScopedFDCloseTraits>, crashpad::ChildPortHandshake::PortRightType) + 516
3   crashpad_handler                    0x00000001040bb926 crashpad::HandlerMain(int, char**, std::__1::vector<std::__1::unique_ptr<crashpad::UserStreamDataSource, std::__1::default_delete<crashpad::UserStreamDataSource> >, std::__1::allocator<std::__1::unique_ptr<crashpad::UserStreamDataSource, std::__1::default_delete<crashpad::UserStreamDataSource> > > > const*) + 4790
4   libdyld.dylib                       0x00007fff9ccc85ad start + 1
[0508/050441.816282:ERROR:file_io.cc(89)] ReadExactly: expected 4, observed 0
[0508/050441.816778:ERROR:mach_extensions.cc(68)] bootstrap_check_in org.chromium.crashpad.child_port_handshake.63984.1016709.LMZRXENREUMFNSXP: unknown error code (141)
[0508/050441.816858:FATAL:child_port_handshake.cc(111)] Check failed: server_port.is_valid().
0   crashpad_handler                    0x000000010c1e26ac base::debug::StackTrace::StackTrace(unsigned long) + 28
1   crashpad_handler                    0x000000010c1cf94f logging::LogMessage::~LogMessage() + 223
[63982:775:0508/050441.818507:24287227641951:ERROR:file_io.cc(89)] ReadExactly: expected 4, observed 0
Received signal 11 SEGV_MAPERR 000000000008

Adding CrashReporting component for folks to take a look. This might also be related to some problem in the bot.

Sample build
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Mac10.11%20Tests/26009

it seems that the last such failure was 26009 (2018-05-08 8:38 PM (CEST)).

Thus, they don't fail frequently enough to be disabled anymore (the last failure was ~40 builds ago), but it would be great if you could have a look anyway.

Adding child_port_handshake.cc OWNERS - mark@, rsesek@.

Could you have a look and probably redirect further?
Could a new version of crashpad have fixed this?