For other platforms, we can wait in WebPage::platformInitialize. This can potentially reduce wait time for these platforms, since the Network process is providing the database, and I believe we always have a Network process when the WebPage is created. The next step is to do the same on macOS, but that requires a little more consideration, and will be done in a follow-up patch.
Created attachment 454884 [details] Patch
<rdar://88933565>