Introduce wrapPersistent()/wrapCrossThreadPersistent()
Introduce wrapPersistent()/wrapCrossThreadPersistent()

These wrappers are for constructing Persistent/CrossThreadPersistent from
raw pointers without writing typenames explicitly.

These will be used by subsequent CLs for Issue 597856.

BUG=597856

Review-Url: https://codereview.chromium.org/1923813002
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#393490}

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