Fix closing of last tab.

If tab was loading when closed, pagestack push didn't happen.
TabModel count and BrowserPage's status are the only variables that
we need to take care here.
Fix ResourceController to handle suspend property when no webView

No webView happens a short period of time during browser
launch and a stable state when all tabs have been closed.

We can emit webViewSuspended also when we don't have webView
as it is only used to close network session.