Issue 5013 - Make parameter const ref when applicable.

test/UpdateCheck.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 68 matching lines @@
 
       filterEngine = AdblockPlus::FilterEngine::Create(jsEngine);
     }
 
     void ForceUpdateCheck()
     {
       filterEngine->ForceUpdateCheck(
           std::bind(&UpdateCheckTest::UpdateCallback, this, std::placeholders::_1));
     }
 
-    void EventCallback(AdblockPlus::JsValueList& params)
+    void EventCallback(const AdblockPlus::JsValueList& params)
     {
       eventCallbackCalled = true;
       eventCallbackParams = params;
     }
 
     void UpdateCallback(const std::string& error)
     {
       updateCallbackCalled = true;
       updateError = error;
     }
@@ skipping 156 matching lines @@
 
   Reset();
   ForceUpdateCheck();
 
   AdblockPlus::Sleep(100);
 
   ASSERT_FALSE(eventCallbackCalled);
   ASSERT_TRUE(updateCallbackCalled);
   ASSERT_FALSE(updateError.empty());
 }