We refactor several of the static creator methods for
SharedStorageEventParams in preparation for adding several new members
to the class.
Bug: 401011862
Change-Id: Idfafcccce0f8ecd3d530e3223fc0036b79efd654
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6351803
Reviewed-by: Yao Xiao <yaoxia@chromium.org>
Commit-Queue: Cammie Smith Barnes <cammie@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1432387}
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