class ScopedAccess

Class that encapsulates acquiring |mutex_| to provide serialized access to ObjectLinker and

Links created from it.

This protects internal data structures of ObjectLinker, |exports_| and |imports_|, and Links

that are referenced under these data structures. i.e. one thread may run AttemptLinking()

while the other invalidates the Link endpoint, which would cause unexpected behavior and

dropped link_resolved callback. Therefore, each ObjectLinker method accessing these data

structures and each Link method modifying internals should hold ScopedAccess to make sure

calls are serialized.