IndexedDB: Check for permission before using IndexedDB from a worker.

IndexedDB: Check for permission before using IndexedDB from a worker.
https://bugs.webkit.org/show_bug.cgi?id=76500

Reviewed by David Levin.

* src/IDBFactoryBackendProxy.cpp:
(WebKit::AllowIndexedDBMainThreadBridge::create):
(WebKit::AllowIndexedDBMainThreadBridge::cancel):
(WebKit::AllowIndexedDBMainThreadBridge::result):
(WebKit::AllowIndexedDBMainThreadBridge::signalCompleted):
(WebKit::AllowIndexedDBMainThreadBridge::AllowIndexedDBMainThreadBridge):
(WebKit::AllowIndexedDBMainThreadBridge::allowIndexedDBTask): Call
webView->permissionClient()->allowIndexedDB on the main thread because
ContentSettingsObserver::AllowIndexedDB(), which is called down the
chain, expects to be run on the main thread.
(WebKit::AllowIndexedDBMainThreadBridge::didComplete):
(WebKit::IDBFactoryBackendProxy::allowIDBFromWorkerThread): Wait for
main permission check to complete on main thread before proceeding on
worker thread.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@105324 268f45cc-cd09-0410-ab3c-d52691b4dbfc