This could look something like this:

dictionary WindowActorOptions {
  // ...

  // Optional list of regular expressions for remoteTypes which are
  // allowed to instantiate this actor. If not passed, all content 
  // processes are allowed to instantiate the actor. 
  sequence<DOMString> remoteTypes;
};

Nika said she'll be adding more pointers for jdai's work here.

This check should be added to the same Matches function which you added in bug 1523982. Information about the remote type which is being considered will have to be passed in as an extra const nsString& aRemoteType parameter.

For a WindowGlobalParent the remote type can be fetched like this:

RefPtr<WindowGlobalParent> wgp = ...;

nsAutoString remoteType;
if (RefPtr<TabParent> tp = wgp->GetTabParent()) {
  remoteType = tp->Manager()->GetRemoteType();
} else {
  remoteType = VoidString();
}

For a WindowGlobalChild, the remote type can be fetched like this:

nsAutoString remoteType;
if (XRE_IsContentProcess()) {
  remoteType = ContentChild::GetSingleton()->GetRemoteType();
} else {
  remoteType = VoidString();
}

The field should be on the WindowActorOptions dictionary:

dictionary WindowActorOptions {
  // ...

  DOMString? remoteType;
};

The type in native will be Optional<nsString>. If WasPassed() is false, we ignore the remoteType, otherwise check that it matches the value retrieved above, and return false otherwise.

Thank you for your valuable input. :)

Depends on D24733

My old patches were base on bug 1523982 since bug 1523982 was landed, I was trying to rebase my patches to central, but it seems that I can't update patches from arc/phlay to different parent, hence, I send new patches for review. Sorry for any inconvenience.

https://hg.mozilla.org/mozilla-central/rev/99c4c6989e06
https://hg.mozilla.org/mozilla-central/rev/28c8708ee20e