Created attachment 142451 [details]
dmesg log

This can replicated every time.
System: Lenovo A485 with 2700U APU
Kernel: 4.20.0-rc2

Steps to replicate:
1. Download Firefox Nightly from nightly.mozilla.org
2. Open Firefox Nightly
3. Type about:config in the address bar and press enter
4. Search for gfx.webrender.all in the config search box and double click the
"gfx.webrender.all" entry enable it (will show enabled after double clicking)
5. Restart Firefox Nightly
6. Browse to http://diana-adrianne.com/purecss-francine/ in Firefox Nightly
7. Screen should stop responding within a few seconds after zooming/scrolling a
bit

Result: Screen will stop responding, though the mouse cursor still moves.

dmesg output:
nov 12 14:42:15 kernel: [drm:amdgpu_job_timedout [amdgpu]] *ERROR* ring sdma0
timeout, signaled seq=20166, emitted seq=20168
nov 12 14:42:15 kernel: [drm] GPU recovery disabled.
nov 12 14:42:35 kernel: [TTM] Buffer eviction failed