Bug 890040 - Part 1: Support multiple obsolete documents IDs in BagheeraClient.
Bug 890040 - Part 2: Record all potentially uploaded IDs for future deletion.
Bug 890040 - Part 3: Build out ObsoleteDocumentTracker API to not expose JSON.
Bug 890040 - Review comment: Factor out TEST_URL.
Bug 890040 - Follow-up: Improve logging of obsoleted IDs.
Bug 890040 - Follow-up: Bound the number of obsolete IDs stored.
Bug 890040 - Review comment: Update limits.
Bug 890040 - Review comment: On local exceptions, don't track id and don't decrement on delete.

A "local exception" is one that cannot create a document on the
server.  These ids that we know don't make it to the server shouldn't
bump (too many) legitimate records from the obsolete document queue.
Bug 890040 - Follow-up: Ensure we don't orphan an ID during migration.
Bug 890040 - pre: Add ExtendedJSONObject.entrySet.
Bug 890040 - Review comment: Give document IDs that we know are on the server priority.
Bug 890040 - Follow-up: Pass id and exception through where necessary.
Bug 890040 - Follow-up: Limit the number of deletions attempted when upload is disabled.