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They're all segfaulting:

[ RUN      ] WatchTimeReporterTest/WatchTimeReporterTest.WatchTimeReporterAutoplayInitiated/1
Received signal 11 SEGV_MAPERR 000000000000
#0 0x55f8b5c0be21 (/b/s/w/ir/out/Release/media_blink_unittests+0x8de1e20)
#1 0x55f8bbb98d4f (/b/s/w/ir/out/Release/media_blink_unittests+0xed6ed4e)
#2 0x55f8bbb97dca (/b/s/w/ir/out/Release/media_blink_unittests+0xed6ddc9)
#3 0x7f3480b3e330 (/lib/x86_64-linux-gnu/libpthread-2.19.so+0x1032f)
#4 0x55f8bb9a2563 (/b/s/w/ir/out/Release/media_blink_unittests+0xeb78562)
#5 0x55f8b60f2761 (/b/s/w/ir/out/Release/media_blink_unittests+0x92c8760)
#6 0x55f8b60f64fa (/b/s/w/ir/out/Release/media_blink_unittests+0x92cc4f9)
#7 0x55f8bb33232b (/b/s/w/ir/out/Release/media_blink_unittests+0xe50832a)
#8 0x55f8bb333ab7 (/b/s/w/ir/out/Release/media_blink_unittests+0xe509ab6)
#9 0x55f8bb35c777 (/b/s/w/ir/out/Release/media_blink_unittests+0xe532776)
#10 0x55f8bb35bad3 (/b/s/w/ir/out/Release/media_blink_unittests+0xe531ad2)
#11 0x55f8bbbf5918 (/b/s/w/ir/out/Release/media_blink_unittests+0xedcb917)
#12 0x55f8b5e24aae (/b/s/w/ir/out/Release/media_blink_unittests+0x8ffaaad)
#13 0x55f8bbbfd9f5 (/b/s/w/ir/out/Release/media_blink_unittests+0xedd39f4)
#14 0x55f8bbbfd49e (/b/s/w/ir/out/Release/media_blink_unittests+0xedd349d)
#15 0x55f8b5e247e7 (/b/s/w/ir/out/Release/media_blink_unittests+0x8ffa7e6)
#16 0x7f347b2fef45 (/lib/x86_64-linux-gnu/libc-2.19.so+0x21f44)
#17 0x55f8b5bbe02a (/b/s/w/ir/out/Release/media_blink_unittests+0x8d94029)
  r8: 00007f34759be000  r9: 00007f34759bd377 r10: 00000c107ffff92e r11: 00007f347b468310
 r12: 0000000000000000 r13: 00000fe68eba59c0 r14: 00007f3475ad1220 r15: 00007f3475d2ce00
  di: 0000000000000000  si: 0000000000000000  bp: 00007ffc4e420130  bx: 00007ffc4e4200c0
  dx: 0000000000000000  ax: f3f3f3f3f3f3f3f8  cx: f8f8f8f8f8f8f8f8  sp: 00007ffc4e4200c0
  ip: 000055f8bb9a2563 efl: 0000000000010246 cgf: 0000000000000033 erf: 0000000000000004
 trp: 000000000000000e msk: 0000000000000000 cr2: 0000000000000000
[end of stack trace]
Calling _exit(1). Core file will not be generated.

But I can't find a symbolized stack anywhere...

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Tried exact bot args and variations, but unable to reproduce locally. Can't addr2line the symbols since there are no debug artifacts uploaded for CQ builds :/

Seems to be the only bot failing and has stopped since 7am... Flakiness dashboard doesn't have any culprits. Stuck without more information to go on.

+martiniss (current trooper) in case there's a short-lived bucket that has CQ artifacts in it that we could use for addr2line on one of the more recent flakes.

https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=media_blink_unittests%20%28with%20patch%29&builder=tryserver.chromium.linux%3Alinux_chromium_asan_rel_ng

Tried checking out a recent hash and using addr2line on that, but unfortunately our builds aren't quite that deterministic yet it appears :/

+asan folks since I would normally expect a crash to print an asan stack trace, but maybe one doesn't get printed for nullptr dereference. 

ASan should have reported this, unless it is disabled with handle_segv=0 in ASAN_OPTIONS (but I don't see it in cs.chromium.org), or something has replaced ASan signal handler.

But ASan report would not contain any new information for a null pointer dereference.

Yes, I was mostly just hoping it would have a symbolized stack trace :)

This hasn't happened recently? (if I can read the FindIt results correctly)

One from today has this CHECK failure in it:
[857:857:1119/094904.709138:4339622575:FATAL:data_resource_helper.cc(38)] Check failed: !data_string.IsEmpty().

https://logs.chromium.org/logs/chromium/buildbucket/cr-buildbucket.appspot.com/8929409890170442640/+/steps/media_blink_unittests__with_patch_/0/logs/BackgroundBehaviorTestInstances__x2f_WebMediaPlayerImplBackgroundBehaviorTest.AudioOnly__x2f_139/0

But that's not the same crash since it doesn't have pthreads in the stack, so I think this one has resolved itself? Flakiness dashboard agrees with you that it hasn't seen it recently otherwise. Closing as WontFix and hope it doesn't reappear.