Testcase found while fuzzing mozilla-central rev e7e658ec1e98.

Testcase bisects to the following range:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=cc2984b1f9f28bc2ab198efd1378db80db36f4d6&tochange=e66a2b59914df9ac0ac6bad9887dc8585575bede

CC'ing :apehrson as it appears he touched the affected file during this range.

==16301==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000001 (pc 0x7f8e11afd2ad bp 0x7ffdf9741390 sp 0x7ffdf97412e0 T0)
==16301==The signal is caused by a WRITE memory access.
==16301==Hint: address points to the zero page.
    #0 0x7f8e11afd2ac in mozilla::MediaEncoder::RunOnGraph(already_AddRefed<mozilla::Runnable>) /builds/worker/workspace/build/src/dom/media/encoder/MediaEncoder.cpp:449:5
    #1 0x7f8e118b2b0f in mozilla::dom::MediaRecorder::Session::Resume() /builds/worker/workspace/build/src/dom/media/MediaRecorder.cpp:467:15
    #2 0x7f8e118b287f in mozilla::dom::MediaRecorder::Resume(mozilla::ErrorResult&) /builds/worker/workspace/build/src/dom/media/MediaRecorder.cpp:1326:42
    #3 0x7f8e0ebd819c in mozilla::dom::MediaRecorder_Binding::resume(JSContext*, JS::Handle<JSObject*>, mozilla::dom::MediaRecorder*, JSJitMethodCallArgs const&) /builds/worker/workspace/build/src/obj-firefox/dom/bindings/MediaRecorderBinding.cpp:1128:24
    #4 0x7f8e109a4aad in bool mozilla::dom::binding_detail::GenericMethod<mozilla::dom::binding_detail::NormalThisPolicy, mozilla::dom::binding_detail::ThrowExceptions>(JSContext*, unsigned int, JS::Value*) /builds/worker/workspace/build/src/dom/bindings/BindingUtils.cpp:3163:13
    #5 0x7f8e17567577 in CallJSNative /builds/worker/workspace/build/src/js/src/vm/Interpreter.cpp:447:13
    #6 0x7f8e17567577 in js::InternalCallOrConstruct(JSContext*, JS::CallArgs const&, js::MaybeConstruct) /builds/worker/workspace/build/src/js/src/vm/Interpreter.cpp:539
    #7 0x7f8e1754f81c in CallFromStack /builds/worker/workspace/build/src/js/src/vm/Interpreter.cpp:598:10
    #8 0x7f8e1754f81c in Interpret(JSContext*, js::RunState&) /builds/worker/workspace/build/src/js/src/vm/Interpreter.cpp:3084
    #9 0x7f8e17530ebf in js::RunScript(JSContext*, js::RunState&) /builds/worker/workspace/build/src/js/src/vm/Interpreter.cpp:424:10
    #10 0x7f8e1756807f in js::InternalCallOrConstruct(JSContext*, JS::CallArgs const&, js::MaybeConstruct) /builds/worker/workspace/build/src/js/src/vm/Interpreter.cpp:567:13
    #11 0x7f8e1756a2a2 in js::Call(JSContext*, JS::Handle<JS::Value>, JS::Handle<JS::Value>, js::AnyInvokeArgs const&, JS::MutableHandle<JS::Value>) /builds/worker/workspace/build/src/js/src/vm/Interpreter.cpp:610:8
    #12 0x7f8e180760d8 in JS::Call(JSContext*, JS::Handle<JS::Value>, JS::Handle<JS::Value>, JS::HandleValueArray const&, JS::MutableHandle<JS::Value>) /builds/worker/workspace/build/src/js/src/jsapi.cpp:2722:10
    #13 0x7f8e1020de10 in mozilla::dom::EventListener::HandleEvent(JSContext*, JS::Handle<JS::Value>, mozilla::dom::Event&, mozilla::ErrorResult&) /builds/worker/workspace/build/src/obj-firefox/dom/bindings/EventListenerBinding.cpp:52:8
    #14 0x7f8e111313b5 in HandleEvent<mozilla::dom::EventTarget *> /builds/worker/workspace/build/src/obj-firefox/dist/include/mozilla/dom/EventListenerBinding.h:66:12
    #15 0x7f8e111313b5 in mozilla::EventListenerManager::HandleEventSubType(mozilla::EventListenerManager::Listener*, mozilla::dom::Event*, mozilla::dom::EventTarget*) /builds/worker/workspace/build/src/dom/events/EventListenerManager.cpp:1033
    #16 0x7f8e11132e30 in mozilla::EventListenerManager::HandleEventInternal(nsPresContext*, mozilla::WidgetEvent*, mozilla::dom::Event**, mozilla::dom::EventTarget*, nsEventStatus*, bool) /builds/worker/workspace/build/src/dom/events/EventListenerManager.cpp:1231:17
    #17 0x7f8e1111998a in HandleEvent /builds/worker/workspace/build/src/obj-firefox/dist/include/mozilla/EventListenerManager.h:353:5
    #18 0x7f8e1111998a in mozilla::EventTargetChainItem::HandleEvent(mozilla::EventChainPostVisitor&, mozilla::ELMCreationDetector&) /builds/worker/workspace/build/src/dom/events/EventDispatcher.cpp:349
    #19 0x7f8e111181a2 in mozilla::EventTargetChainItem::HandleEventTargetChain(nsTArray<mozilla::EventTargetChainItem>&, mozilla::EventChainPostVisitor&, mozilla::EventDispatchingCallback*, mozilla::ELMCreationDetector&) /builds/worker/workspace/build/src/dom/events/EventDispatcher.cpp:551:16
    #20 0x7f8e1111db6b in mozilla::EventDispatcher::Dispatch(nsISupports*, nsPresContext*, mozilla::WidgetEvent*, mozilla::dom::Event*, nsEventStatus*, mozilla::EventDispatchingCallback*, nsTArray<mozilla::dom::EventTarget*>*) /builds/worker/workspace/build/src/dom/events/EventDispatcher.cpp:1047:11
    #21 0x7f8e13ac7144 in nsDocumentViewer::LoadComplete(nsresult) /builds/worker/workspace/build/src/layout/base/nsDocumentViewer.cpp:1169:7
    #22 0x7f8e166f4f49 in nsDocShell::EndPageLoad(nsIWebProgress*, nsIChannel*, nsresult) /builds/worker/workspace/build/src/docshell/base/nsDocShell.cpp:6519:20
    #23 0x7f8e166f41ee in nsDocShell::OnStateChange(nsIWebProgress*, nsIRequest*, unsigned int, nsresult) /builds/worker/workspace/build/src/docshell/base/nsDocShell.cpp:6319:7
    #24 0x7f8e166f8d3f in non-virtual thunk to nsDocShell::OnStateChange(nsIWebProgress*, nsIRequest*, unsigned int, nsresult) /builds/worker/workspace/build/src/docshell/base/nsDocShell.cpp
    #25 0x7f8e0ca8b65c in nsDocLoader::DoFireOnStateChange(nsIWebProgress*, nsIRequest*, int&, nsresult) /builds/worker/workspace/build/src/uriloader/base/nsDocLoader.cpp:1333:3
    #26 0x7f8e0ca8a6fc in nsDocLoader::doStopDocumentLoad(nsIRequest*, nsresult) /builds/worker/workspace/build/src/uriloader/base/nsDocLoader.cpp:892:14
    #27 0x7f8e0ca8631b in nsDocLoader::DocLoaderIsEmpty(bool) /builds/worker/workspace/build/src/uriloader/base/nsDocLoader.cpp:726:9
    #28 0x7f8e0ca89176 in nsDocLoader::OnStopRequest(nsIRequest*, nsresult) /builds/worker/workspace/build/src/uriloader/base/nsDocLoader.cpp:614:5
    #29 0x7f8e0ca8a2dc in non-virtual thunk to nsDocLoader::OnStopRequest(nsIRequest*, nsresult) /builds/worker/workspace/build/src/uriloader/base/nsDocLoader.cpp
    #30 0x7f8e0a31c870 in mozilla::net::nsLoadGroup::RemoveRequest(nsIRequest*, nsISupports*, nsresult) /builds/worker/workspace/build/src/netwerk/base/nsLoadGroup.cpp:568:22
    #31 0x7f8e0e21a3b1 in DoUnblockOnload /builds/worker/workspace/build/src/dom/base/Document.cpp:10671:18
    #32 0x7f8e0e21a3b1 in mozilla::dom::nsUnblockOnloadEvent::Run() /builds/worker/workspace/build/src/dom/base/Document.cpp:10627
    #33 0x7f8e0a0355d1 in mozilla::SchedulerGroup::Runnable::Run() /builds/worker/workspace/build/src/xpcom/threads/SchedulerGroup.cpp:295:32
    #34 0x7f8e0a067520 in nsThread::ProcessNextEvent(bool, bool*) /builds/worker/workspace/build/src/xpcom/threads/nsThread.cpp:1225:14
    #35 0x7f8e0a06d568 in NS_ProcessNextEvent(nsIThread*, bool) /builds/worker/workspace/build/src/xpcom/threads/nsThreadUtils.cpp:486:10
    #36 0x7f8e0b261fef in mozilla::ipc::MessagePump::Run(base::MessagePump::Delegate*) /builds/worker/workspace/build/src/ipc/glue/MessagePump.cpp:88:21
    #37 0x7f8e0b15d052 in RunInternal /builds/worker/workspace/build/src/ipc/chromium/src/base/message_loop.cc:315:10
    #38 0x7f8e0b15d052 in RunHandler /builds/worker/workspace/build/src/ipc/chromium/src/base/message_loop.cc:308
    #39 0x7f8e0b15d052 in MessageLoop::Run() /builds/worker/workspace/build/src/ipc/chromium/src/base/message_loop.cc:290
    #40 0x7f8e133daad9 in nsBaseAppShell::Run() /builds/worker/workspace/build/src/widget/nsBaseAppShell.cpp:137:27
    #41 0x7f8e172aef7f in XRE_RunAppShell() /builds/worker/workspace/build/src/toolkit/xre/nsEmbedFunctions.cpp:934:20
    #42 0x7f8e0b15d052 in RunInternal /builds/worker/workspace/build/src/ipc/chromium/src/base/message_loop.cc:315:10
    #43 0x7f8e0b15d052 in RunHandler /builds/worker/workspace/build/src/ipc/chromium/src/base/message_loop.cc:308
    #44 0x7f8e0b15d052 in MessageLoop::Run() /builds/worker/workspace/build/src/ipc/chromium/src/base/message_loop.cc:290
    #45 0x7f8e172ae826 in XRE_InitChildProcess(int, char**, XREChildData const*) /builds/worker/workspace/build/src/toolkit/xre/nsEmbedFunctions.cpp:769:34
    #46 0x5603d0820d73 in content_process_main /builds/worker/workspace/build/src/browser/app/../../ipc/contentproc/plugin-container.cpp:56:28
    #47 0x5603d0820d73 in main /builds/worker/workspace/build/src/browser/app/nsBrowserApp.cpp:267
    #48 0x7f8e2b77bb96 in __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:310

Bugbug thinks this bug is a regression, but please revert this change in case of error.

Depends on D45194

Regression from https://hg.mozilla.org/mozilla-central/rev/9e6eddfb4ef87865a15258f35eaab0635d197b4e

https://hg.mozilla.org/mozilla-central/rev/9e517b69b1b6
https://hg.mozilla.org/mozilla-central/rev/7a17b2a9a3d4

Comment on attachment 9091450 [details]
Bug 1575271 - Keep a SharedDummyStream in MediaEncoder for access to the MediaStreamGraph. r?karlt

Beta/Release Uplift Approval Request

• User impact if declined: Firefox can be crashed at the will of an attacker
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): Simple enough
• String changes made/needed:

Comment on attachment 9091450 [details]
Bug 1575271 - Keep a SharedDummyStream in MediaEncoder for access to the MediaStreamGraph. r?karlt

Avoids a potential crash, let's try it on beta 7.

https://hg.mozilla.org/releases/mozilla-beta/rev/7a2c20bfec72
https://hg.mozilla.org/releases/mozilla-beta/rev/705b2a73e8f4

There have been considerable changes since 68, making this hard to uplift to esr68. Most notably bug 1014393, which is too big and risky to uplift.