Bug 309386 – [IndexedDB] Recover IndexedDB connections after network process crash without page reload

• Component: WebCore Misc.
• Status: RESOLVED FIXED

[Brandon]

When the NetworkProcess crashes, IndexedDB becomes permanently broken for the
lifetime of the page. Documents and workers cache an IDBConnectionProxy pointing                                                                                                            
to a dead IDBConnectionToServer (m_serverConnectionIsValid == false), and the                                                                                                             
DOMWindowIndexedDatabase/WorkerGlobalScopeIndexedDatabase supplements cache an
IDBFactory bound to that dead proxy. New indexedDB.open() calls fail with
"Connection to Indexed Database server lost" until the page is reloaded.

Fix this by clearing the stale proxy caches when the network process connection
is lost:

- Document::clearIDBConnectionProxy() nulls m_idbConnectionProxy so the next
  idbConnectionProxy() call lazily fetches a fresh proxy from Page::idbConnection(),
  and removes the DOMWindowIndexedDatabase supplement so the IDBFactory is recreated.

- Page::clearIDBConnectionOnAllDocuments() clears the page-level IDBConnectionToServer
  and all document proxies.

- For workers, Page::refreshIDBConnectionForWorkers() creates a new IDBConnectionToServer
  and distributes its proxy to all worker threads via
  WorkerGlobalScope::replaceIDBConnectionProxyOnAllWorkers(), which iterates
  allWorkerGlobalScopeIdentifiers and posts a task to each worker to replace its
  cached proxy and remove its WorkerGlobalScopeIndexedDatabase supplement.

- NetworkProcessConnection::didClose() calls refreshIDBConnectionForWorkers() after
  connectionToServerLost() finishes tearing down the old connection, so workers
  receive the new proxy after all error notifications from the old connection.

- Supplementable::removeSupplement() is added to support clearing cached supplements.

[Radar WebKit Bug Importer]

<rdar://problem/171932720>

[Brandon]

Pull request: https://github.com/WebKit/WebKit/pull/60094

[EWS]

Committed 309032@main (3c147a650200): <https://commits.webkit.org/309032@main>

Reviewed commits have been landed. Closing PR #60094 and removing active labels.