Issue 5137 - [emscripten] Added basic filter storage implementation

compiled/subscription/Subscription.cpp

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 10 matching lines @@
 #include "Subscription.h"
 #include "DownloadableSubscription.h"
 #include "UserDefinedSubscription.h"
 #include "../StringMap.h"
 
 namespace
 {
   StringMap<Subscription*> knownSubscriptions(16);
 }
 
+class DownloadableSubscription;
+class UserDefinedSubscription;
+
 Subscription::Subscription(Type type, const String& id)
     : mID(id), mType(type), mDisabled(false)
 {
   annotate_address(this, "Subscription");
 }
 
 Subscription::~Subscription()
 {
   knownSubscriptions.erase(mID);
 }
@@ skipping 81 matching lines @@
 
   // This is a hack: we looked up the entry using id but create it using
   // subscription->mID. This works because both are equal at this point.
   // However, id refers to a temporary buffer which will go away.
   enter_context("Adding to known subscriptions");
   knownSubscription.assign(subscription->mID, subscription.get());
   exit_context();
 
   return subscription.release();
 }