graphite: Do not initialize WebGL CRP using Skia

Graphite won't support bottom left origin SkSurfaces or rendering.
WebGL context CanvasResourceProvider has the same origin as the context
which is bottom left most of the time (except when mesa framebuffer flip
extension is used). This CRP is initialized/cleared using Skia which
won't work with Graphite for bottom left origin, and is unnecessary
anyway since the WebGL context is responsible for rendering into it and
clearing it. The shared image clear rect tracking should enforce this.

Bug: 1456636
Change-Id: Ic9507ae352a42b1ca9698b6ca978e610fb03a7e3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4632398
Commit-Queue: Sunny Sachanandani <sunnyps@chromium.org>
Auto-Submit: Sunny Sachanandani <sunnyps@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1160977}