[RESTRICT AUTOMERGE]: Stop discarding stencil buffers on tilers
[RESTRICT AUTOMERGE]: Stop discarding stencil buffers on tilers

Bug: b/160958008
Test: SystemWebViewShell.apk
      - Tap 3 dot menu
      - Tap "Animation test"
      - Check "Rounded corner" checkbox
Change-Id: I67851cb4be1a95f9f1d813846f5d4ba4b1535d9c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/304176
Reviewed-by: Chris Dalton <ef7fc3a08ada7d31f16e9a18b5f3c728256e041e@google.com>

aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia