Improve Dispose

[amaitland]

There are two Dispose scenarios:

1. User initiated
   • Needs to send the relevant DevTools commands so a new DevToolsContext can be created later if required.
   • Unhook events
   • Dispose of DevTools observer
2. ChromiumWebBrowser Dispose
   • Unhook events

For scenario #2 as the browser is disposing it's difficult and likely not necessary to send the DevTools commands

[amaitland]

CEF will internally call IDevToolsMessageObserver.Dispose when the browser is shutting down, so there's no need to explicitly Dispose of the IDevToolsMessageObserver, it should be possible to use this to handle case #2 properly, should be sufficient to unwire the event handlers and let the DevToolsContext know that it's been Disposed.

[amaitland]

CEF will internally call IDevToolsMessageObserver.Dispose when the browser is shutting down, so there's no need to explicitly Dispose of the IDevToolsMessageObserver, it should be possible to use this to handle case #2 properly, should be sufficient to unwire the event handlers and let the DevToolsContext know that it's been Disposed.

Further testing and it appears that Dispose was being called as a result of IRegistration.Dispose being called. An alternative might be IDevToolsMessageObserver.OnDevToolsAgentDetached which is called as expected, just need to check if it's called only for our message observer or for all registered.

[amaitland]

Version 2.0.83 includes these changes.