Allow creating new windows from a notificationclick event in SW.

Source/modules/serviceworkers/ServiceWorkerGlobalScope.h

Index: Source/modules/serviceworkers/ServiceWorkerGlobalScope.h
diff --git a/Source/modules/serviceworkers/ServiceWorkerGlobalScope.h b/Source/modules/serviceworkers/ServiceWorkerGlobalScope.h
index f077fc4b6b9aa79bf9371fcc5e1414c86093d3e8..48e8cccfaaec78a68a686944b3e3ed04e0599e2d 100644
--- a/Source/modules/serviceworkers/ServiceWorkerGlobalScope.h
+++ b/Source/modules/serviceworkers/ServiceWorkerGlobalScope.h
@@ -93,6 +93,10 @@ public:
 
     virtual void trace(Visitor*) override;
 
+    // Timeout before a service worker that was given window interaction
+    // permission loses them. The unit is seconds.
+    static const int kWindowInteractionTimeout = 10;
+
 private:
     class SkipWaitingCallback;