[Blink] Move test into CanvasRenderingContext2D tests

We will be eliminating CanvasResourceHost having knowledge of the CC
layer entirely.

Note: Adding this test requires that the relevant text fixture create
composited canvases, which is the reason for che changes to the fixture
in this CL.

Bug: 399587138
Change-Id: I56f989ad4e310128476e8c4059ed63ad8e503592
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6544788
Reviewed-by: Vasiliy Telezhnikov <vasilyt@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1460522}