crash log for renderer (pid <unknown>):
STDOUT: #CRASHED - renderer
STDERR: ASSERTION FAILED: !node || node->isUnused()
STDERR: ../../third_party/WebKit/Source/platform/heap/PersistentNode.h(76) : blink::PersistentNode *blink::PersistentNode::freeListNext()
STDERR: 1   0x7fd26086a693
STDERR: 2   0x7fd26086a0e1
STDERR: 3   0x7fd2608a5658
STDERR: 4   0x7fd260efa737
STDERR: 5   0x7fd260efac50
STDERR: 6   0x7fd260efac08
STDERR: 7   0x7fd260efad70
STDERR: 8   0x7fd260efacce
STDERR: 9   0x7fd260efab07
STDERR: 10  0x7fd260efaa32
STDERR: 11  0x7fd260efa8af
STDERR: 12  0x7fd260ef9fde
STDERR: 13  0x7fd260ef9885 blink::MainThreadTaskRunner::postTaskInternal(blink::WebTraceLocation const&, WTF::PassOwnPtr<blink::ExecutionContextTask>, bool)
STDERR: 14  0x7fd260ef9a9d blink::MainThreadTaskRunner::postTask(blink::WebTraceLocation const&, WTF::PassOwnPtr<blink::ExecutionContextTask>)
STDERR: 15  0x7fd260e50b29 blink::Document::postTask(blink::WebTraceLocation const&, WTF::PassOwnPtr<blink::ExecutionContextTask>)
STDERR: 16  0x7fd2619b4d4a blink::InProcessWorkerObjectProxy::postTaskToMainExecutionContext(WTF::PassOwnPtr<blink::ExecutionContextTask>)
STDERR: 17  0x7fd2619ab165 blink::DedicatedWorkerGlobalScope::countFeature(blink::UseCounter::Feature) const
STDERR: 18  0x7fd26170af9f blink::UseCounter::count(blink::ExecutionContext const*, blink::UseCounter::Feature)
STDERR: 19  0x7fd26090708c blink::V8PerIsolateData::useCounterCallback(v8::Isolate*, v8::Isolate::UseCounterFeature)
STDERR: 20  0x7fd2656f5dba
STDERR: 21  0x7fd2657a77da
STDERR: 22  0x7fd2657a7a77
STDERR: 23  0x7fd2657a78f9
STDERR: 24  0x7fd2653c24d3
STDERR: 25  0x7fd2653bfbbd
STDERR: 26  0x7fd26583796a
STDERR: 27  0x7fd265837730
STDERR: 28  0x28a482908b27
STDERR: [24362:24377:0509/215325:7047376488178:WARNING:crash_handler_host_linux.cc(293)] Could not translate tid - assuming crashing thread is thread group leader; syscall_supported=1