Remove NOTREACHED in PaintRenderingResultsToCanvas.

It calls CopyRenderingResultsFromDrawingBuffer, which handles both the
accelerated and software cases. If that fails, there's no further
fallback possible, so return false and don't call NOTREACHED.

Bug: 1410459
Change-Id: Ic47ee3f50be5576afb62aac557a0703aed1ee1ad
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4347918


Reviewed-by: Austin Eng <enga@chromium.org>
Auto-Submit: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Austin Eng <enga@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1118908}