Remove PR_DetachThread from multi_threaded_cert_verifier.

PR_DetachThread is not necessary, because Chromium code
never calls PR_Cleanup (which requires threads be cleaned up
beforehand), and the thread-specific data itself will be
cleaned up by NSPR's pthreads hook. However, PR_DetachThread
can cause a crash if NSS hasn't been initialized at all
(e.g. with use_byte_certs=true in unittests), so it's not
just unnecessary, but actively harmful.

Bug: 671420
Change-Id: I294ac988c53c7b5109b80eec2aef547cb46f650a
Reviewed-on: https://chromium-review.googlesource.com/558605Reviewed-by: Ryan Sleevi <rsleevi@chromium.org>
Commit-Queue: Matt Mueller <mattm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488734}

net/cert/multi_threaded_cert_verifier.cc

@@ -36,10 +36,6 @@
 #include "net/log/net_log_source_type.h"
 #include "net/log/net_log_with_source.h"
 
-#if defined(USE_NSS_CERTS)
-#include <private/pprthred.h>  // PR_DetachThread
-#endif
-
 namespace net {
 
 class NetLogCaptureMode;
@@ -193,17 +189,6 @@ void DoVerifyOnWorkerThread(const scoped_refptr<CertVerifyProc>& verify_proc,
   TRACE_EVENT0(kNetTracingCategory, "DoVerifyOnWorkerThread");
   *error = verify_proc->Verify(cert.get(), hostname, ocsp_response, flags,
                                crl_set.get(), additional_trust_anchors, result);
-
-#if defined(USE_NSS_CERTS)
-  // Detach the thread from NSPR.
-  // Calling NSS functions attaches the thread to NSPR, which stores
-  // the NSPR thread ID in thread-specific data.
-  // The threads in our thread pool terminate after we have called
-  // PR_Cleanup.  Unless we detach them from NSPR, net_unittests gets
-  // segfaults on shutdown when the threads' thread-specific data
-  // destructors run.
-  PR_DetachThread();
-#endif
 }
 
 // CertVerifierJob lives only on the verifier's origin message loop.