Bug 1493655 - make nsISecureBrowserUI initialize from a docshell instead of a window, r=keeler,nika

This also removes the (afaict, unused) stub implementation from TabParent. The netwerk header
inclusions were necessary because those files included TabParent.h and through it,
nsISecureBrowserUI, but now TabParent.h no longer does that.

Differential Revision: https://phabricator.services.mozilla.com/D6829

docshell/base/nsDocShell.cpp

@@ -2251,7 +2251,6 @@ nsDocShell::SetSecurityUI(nsISecureBrowserUI* aSecurityUI)
   MOZ_ASSERT(!mIsBeingDestroyed);
 
   mSecurityUI = aSecurityUI;
-  mSecurityUI->SetDocShell(this);
   return NS_OK;
 }