Fix canvas2d context restoration for software CRPSI

In CPU compositing mode, HTMLCanvasElement uses a software
CanvasResourceProviderSharedImage. Context loss detection was
implemented for this provider type, but not context restoration.
For instance, CanvasRenderingContext2D::Restore() would early abort
on an `if (host->GetRasterMode() == RasterMode::kCPU)`. This CL
fixes restoration for this configuration by waiting for
`SharedGpuContext::ContextProviderWrapper` to be healthy before
retrying to create the provider.

Bug: 404257881
Change-Id: I46da47174529b4291a5bf61c1420c0657f5c3128
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6361727
Commit-Queue: Jean-Philippe Gravel <jpgravel@chromium.org>
Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Vasiliy Telezhnikov <vasilyt@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1441188}