crash log for renderer (pid 63772):
STDOUT: <empty>
STDERR: ASSERTION FAILED: headerValueCategoryHistogramStaticLocalVerifier.isNotRacy()
STDERR: ../../third_party/WebKit/Source/core/xmlhttprequest/XMLHttpRequest.cpp(1209) : void blink::XMLHttpRequest::setRequestHeaderInternal(const WTF::AtomicString &, const WTF::AtomicString &)
STDERR: 1   0x10a50d99c blink::XMLHttpRequest::send(WTF::String const&, blink::ExceptionState&)
STDERR: 2   0x10a50d60a blink::XMLHttpRequest::send(blink::ArrayBufferOrArrayBufferViewOrBlobOrDocumentOrStringOrFormData const&, blink::ExceptionState&)
STDERR: 3   0x10a83e50a blink::XMLHttpRequestV8Internal::sendMethodCallback(v8::FunctionCallbackInfo<v8::Value> const&)
STDERR: 4   0x108fa683c v8::internal::FunctionCallbackArguments::Call(void (*)(v8::FunctionCallbackInfo<v8::Value> const&))
STDERR: 5   0x108fe6430 v8::internal::MaybeHandle<v8::internal::Object> v8::internal::(anonymous namespace)::HandleApiCallHelper<false>(v8::internal::Isolate*, v8::internal::(anonymous namespace)::BuiltinArguments<(v8::internal::BuiltinExtraArguments)1>)
STDERR: 6   0x108ffc315 v8::internal::Builtin_HandleApiCall(int, v8::internal::Object**, v8::internal::Isolate*)
STDERR: 7   0x1eaf17c089db
STDERR: Received signal 11 SEGV_MAPERR 0000fbadbeef
STDERR:  [0x000107b5b4ca]
STDERR:  [0x7fff875e85aa]
STDERR:  [0x2f656372756f532f]
STDERR:  [0x00010a50d99c]
STDERR:  [0x00010a50d60a]
STDERR:  [0x00010a83e50a]
STDERR:  [0x000108fa683c]
STDERR:  [0x000108fe6430]
STDERR:  [0x000108ffc315]
STDERR:  [0x1eaf17c089db]
STDERR: [end of stack trace]