Dawn: fix Device leak in DawnTestContext.
Dawn: fix Device leak in DawnTestContext.

The C WGPUDevice returned by CreateDevice needs an Acquire call to
ensure it's correctly refcounted.

Bug: skia:10291

Change-Id: If5d917165b5846bea1472f24aa12db2db7f3a9e6
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/292958
Reviewed-by: Greg Daniel <39df0a804564ccb6cf75f18db79653821f37c1c5@google.com>
Commit-Queue: Stephen White <30b0ee0ef1651e8ba59cfd41f16e23abfe9aca8a@chromium.org>

google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia