This bug was filed from the Socorro interface and is report bp-bb2c988a-40ff-4d0b-831b-2ad150180922. ============================================================= Top 10 frames of crashing thread: 0 firefox-bin mozalloc_abort memory/mozalloc/mozalloc_abort.cpp:35 1 firefox-bin abort memory/mozalloc/mozalloc_abort.cpp:82 2 libxul.so panic_abort::__rust_start_panic::abort src/libpanic_abort/lib.rs:61 3 libxul.so __rust_start_panic src/libpanic_abort/lib.rs:56 4 libxul.so std::panicking::rust_panic_with_hook src/libstd/panicking.rs:523 5 libxul.so std::panicking::continue_panic_fmt src/libstd/panicking.rs:390 6 libxul.so rust_begin_unwind src/libstd/panicking.rs:325 7 libxul.so core::panicking::panic_fmt src/libcore/panicking.rs:77 8 libxul.so core::option::expect_failed src/libcore/option.rs:989 9 libxul.so webrender::texture_cache::TextureCache::get src/libcore/option.rs:312 =============================================================

I could reproduce this or a hang by : going to Youtube. waiting a bit for the add, click pass. Seek , seek. pause. When you want to unpause it either crashes with this or hangs and I need to kill firefox. the full trace looks like this : [Child 6933, MediaPlayback #3] WARNING: Decoder=7f9cee0da180 Decode error: NS_ERROR_DOM_MEDIA_FATAL_ERR (0x806e0005) - RefPtr<MediaSourceTrackDemuxer::SamplesPromise> mozilla::MediaSourceTrackDemuxer::DoGetSamples(int32_t): manager is detached.: file /builds/worker/workspace/build/src/dom/media/MediaDecoderStateMachine.cpp, line 3429 [Child 6933, MediaPlayback #1] WARNING: Decoder=7f9cee0da180 Decode error: NS_ERROR_DOM_MEDIA_FATAL_ERR (0x806e0005) - RefPtr<MediaSourceTrackDemuxer::SamplesPromise> mozilla::MediaSourceTrackDemuxer::DoGetSamples(int32_t): manager is detached.: file /builds/worker/workspace/build/src/dom/media/MediaDecoderStateMachine.cpp, line 3429 [Child 6933, MediaPlayback #1] WARNING: Decoder=7f9cee0da180 Decode error: NS_ERROR_DOM_MEDIA_FATAL_ERR (0x806e0005) - RefPtr<MediaSourceTrackDemuxer::SamplesPromise> mozilla::MediaSourceTrackDemuxer::DoGetSamples(int32_t): manager is detached.: file /builds/worker/workspace/build/src/dom/media/MediaDecoderStateMachine.cpp, line 3429 thread 'WRRenderBackend#1' panicked at 'BUG: was dropped from cache or not updated!', libcore/option.rs:989:5 stack backtrace: 0: 0x7f052dabff82 - std::sys::unix::backtrace::tracing::imp::unwind_backtrace::hced3a4ed290bc7f5 1: 0x7f052dab20de - std::panicking::default_hook::{{closure}}::h15181aeeb7b4bc75 2: 0x7f052dab15ef - std::panicking::default_hook::h63ab9a1a074f1506 3: 0x7f052dab120e - std::panicking::rust_panic_with_hook::hba05450791beb933 4: 0x7f052dab31bd - std::panicking::continue_panic_fmt::hd2a4220d2e2291e2 5: 0x7f052dab3165 - rust_begin_unwind 6: 0x7f052dacf35b - core::panicking::panic_fmt::h2c383e888dce42c0 7: 0x7f052dacf461 - core::option::expect_failed::h7d982926f8026caa 8: 0x7f052d671341 - webrender::texture_cache::TextureCache::get::h627df05e49c90c78 9: 0x7f052d671254 - webrender::resource_cache::ResourceCache::get_cached_image::h8481cd9b5a86c715 10: 0x7f052d660352 - webrender::frame_builder::FrameBuilder::build::h1e290903ebe05fd8 11: 0x7f052d63e4be - webrender::render_backend::Document::build_frame::hcab90e1697fe7311 12: 0x7f052d616836 - webrender::render_backend::RenderBackend::update_document::hdf9ff6e096a2c478 13: 0x7f052d60b127 - webrender::render_backend::RenderBackend::run::h944c0781537a471a 14: 0x7f052d60748e - std::sys_common::backtrace::__rust_begin_short_backtrace::hbb372189df282cdb 15: 0x7f052d60695b - <F as alloc::boxed::FnBox<A>>::call_box::h4962d4231d0e58ec 16: 0x7f052dab38e1 - std::sys::unix::thread::Thread::new::thread_start::ha15fdd35f58285a3 17: 0x7f053a170593 - start_thread 18: 0x7f0539159e6e - clone 19: 0x0 - <unknown>