Bug 1373675 - Add hasListenerFor to nsIWebSocketEventService. r=mcmanus

This makes it possible to check if a Window has 'active' WebSockets.

netwerk/protocol/websocket/WebSocketEventService.cpp

@@ -440,6 +440,17 @@ WebSocketEventService::RemoveListener(uint64_t aInnerWindowID,
   return NS_OK;
 }
 
+NS_IMETHODIMP
+WebSocketEventService::HasListenerFor(uint64_t aInnerWindowID,
+                                      bool* aResult)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  *aResult = mWindows.Get(aInnerWindowID);
+
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 WebSocketEventService::Observe(nsISupports* aSubject, const char* aTopic,
                                const char16_t* aData)

netwerk/protocol/websocket/nsIWebSocketEventService.idl

@@ -76,4 +76,6 @@ interface nsIWebSocketEventService : nsISupports
 
   [must_use] void removeListener(in unsigned long long aInnerWindowID,
                                  in nsIWebSocketEventListener aListener);
+
+  [must_use] bool hasListenerFor(in unsigned long long aInnerWindowID);
 };