I wonder if Bug 1778560 and Bug 1776581 might be related to the bug. At first, wait at RenderCompositorANGLE::WaitForGPU() happened on both bugs, then Bug 1793388 disabled a wait at RenderCompositorANGLE::WaitForGPU() on Windows nightly. But the problem of Bug 1792015 still happens. Then asking to a reporter for taking profile.
Bug 1796511 Comment 1 Edit History
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I wonder if Bug 1778560 and Bug 1792015 might be related to the bug. At first, wait at RenderCompositorANGLE::WaitForGPU() happened on both bugs, then Bug 1793388 disabled a wait at RenderCompositorANGLE::WaitForGPU() on Windows nightly. But the problem of Bug 1792015 still happens. Then asking to a reporter for taking profile.