GitLab

requests.

For StartSession, PSImpl keeps a queue of StartSession requests to be
processed. (It can only process one at a time). If the queue has
reached maximum allowed size (10), subsequent incoming requests will
be immediately rejected.

For Joinsession, PSImpl keeps a map of currently JoinSession requests
that are currently processed. If the map reached maximum allowed size
(10), subsequent incoming requests will be immediately rejected.

Also, tried to simplify some of the cleanup flow for
NewSessionMojoCallbacks by introducing a wrapper class that ensures
callbacks are not dropped. Currently the cleanup logic is sprinkled
all over the file so hopefully this makes things cleaner.

We could generalize the callback wrapper pattern in the future if
it makes necessary.

BUG=412331

Review URL: https://codereview.chromium.org/1141683002

Cr-Commit-Position: refs/heads/master@{#330203}