Enable WebGPUUseTintIR by default on ChromeOS

The metrics look good and we are preparing to launch the new SPIR-V
backend by default on all Vulkan platforms.

Bug: 40284020
Change-Id: I47d1d679e38eb650ce18ea395853b8f90f593394
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5604988


Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: James Price <jrprice@google.com>
Cr-Commit-Position: refs/heads/main@{#1312287}