Dawn: skip PromiseImageShutdownTest and TextureIdleProcTest.

These tests create a wgpu::Texture which outlives the  wgpu::Device
which created it. This is problematic on Dawn, so just skip
the tests for now.

Bug: skia:10326
Change-Id: I29d5328e313baca19a2bbc2eedd80f2768cae77e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/293936
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>
2 files changed