Shared Storage: Add iframe web test for header in sandboxed frame
We add a web test for using shared storage via the shared-storage-
writable response header for an iframe request in a sandboxed iframe.
Bug: 338608329
Change-Id: I94a771e49daa9b44844e931d89eee901c9931e5f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5513004
Commit-Queue: Cammie Smith Barnes cammie@chromium.org
Reviewed-by: Yao Xiao yaoxia@chromium.org
Cr-Commit-Position: refs/heads/main@{#1296932}