Background: 
https://chromium-review.googlesource.com/c/chromium/src/+/1030033/12/services/network/public/mojom/network_service.mojom#188 had to be reverted because it passed 
a base::File() to this method in NetworkContextTest.CreateNetLogExporterErrors, and the signature has it as non-nullable, so it hits:

[10012:10012:0430/152600.891824:1824953923:FATAL:network_service.mojom.cc(307)] The outgoing message will trigger VALIDATION_ERROR_UNEXPECTED_NULL_POINTER at the receiving side (null destination in NetLogExporter.Start request).
#0 0x7f462fe7b5cd base::debug::StackTrace::StackTrace()
#1 0x7f462fbab85c base::debug::StackTrace::StackTrace()
#2 0x7f462fc17d7d logging::LogMessage::~LogMessage()
#3 0x0000012aa48a network::mojom::NetLogExporterProxy_Start_Message::Serialize()
#4 0x7f463025cba2 mojo::(anonymous namespace)::SerializeUnserializedContext()
#5 0x7f462be6c25a mojo::edk::UserMessageImpl::SerializeIfNecessary()
#6 0x7f462be097c4 mojo::edk::Core::SerializeMessage()
#7 0x7f462bdfe094 MojoSerializeMessageImpl
#8 0x7f46302466ac MojoSerializeMessage
#9 0x7f463025bd03 mojo::Message::SerializeIfNecessary()
#10 0x7f462bad234d network::mojom::NetLogExporterStubDispatch::AcceptWithResponder()
#11 0x7f462ba095d1 network::mojom::NetLogExporterStub<>::AcceptWithResponder()


... Which is logical enough.


Problem:
This DCHECK does not seem to trigger on debug builds with is_component_build = false