ImageBitmap::PrepareForDrawTarget overwrites its surface's contents when premultiplying the
data. This code pattern seems to stem all the way back to bug 1239752. It doesn't seem like
we have much control over where this surface comes from, and we have no strong guarantees
that this surface isn't shared by multiple consumers. As such, overwriting the data could
result in another consumer getting premultiplied data in the surface that it didn't expect.
We should just always be cloning the surface first before premultiplying unless we can
otherwise prove the surface isn't shared.
* * *
Bug 1739454 - Remove reftest-wait in reftest. r?emilio
Differential Revision: https://phabricator.services.mozilla.com/D131583
