Issue 5275 - Minimize memory usage as soon as possible

src/JsEngine.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 77 matching lines @@
   isolate->Dispose();
   isolate = nullptr;
 }
 
 JsEngine::JsWeakValuesList::~JsWeakValuesList()
 {
   for (auto& value : values)
     value->Dispose();
 }
 
+void JsEngine::NotifyLowMemory()
+{
+  const JsContext context(*this);
+  v8::V8::LowMemoryNotification();
+}
+
 void JsEngine::ScheduleTimer(const v8::Arguments& arguments)
 {
   auto jsEngine = FromArguments(arguments);
   if (arguments.Length() < 2)
     throw std::runtime_error("setTimeout requires at least 2 parameters");
 
   if (!arguments[0]->IsFunction())
     throw std::runtime_error("First argument to setTimeout must be a function");
 
   auto jsValueArguments = jsEngine->ConvertArguments(arguments);
@@ skipping 228 matching lines @@
   logSystem = val;
 }
 
 
 void AdblockPlus::JsEngine::SetGlobalProperty(const std::string& name,
                                               const AdblockPlus::JsValue& value)
 {
   auto global = GetGlobalObject();
   global.SetProperty(name, value);
 }