Issue 5013 - Make parameter const ref when applicable.

test/BaseJsTest.h

 /*
  * 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 22 matching lines @@
 };
 
 class ThrowingFileSystem : public AdblockPlus::FileSystem
 {
 public:
   std::shared_ptr<std::istream> Read(const std::string& path) const
   {
     throw std::runtime_error("Not implemented");
   }
 
-  void Write(const std::string& path, const std::istream& content)
+  void Write(const std::string& path, std::istream& content)
   {
     throw std::runtime_error("Not implemented");
   }
 
   void Move(const std::string& fromPath, const std::string& toPath)
   {
     throw std::runtime_error("Not implemented");
   }
 
   void Remove(const std::string& path)
@@ skipping 28 matching lines @@
   std::shared_ptr<std::istream> Read(const std::string& path) const
   {
     std::string dummyData("");
     if (path == "patterns.ini")
       dummyData = "# Adblock Plus preferences\n[Subscription]\nurl=~fl~";
     else if (path == "prefs.json")
       dummyData = "{}";
     return std::shared_ptr<std::istream>(new std::istringstream(dummyData));
   }
 
-  void Write(const std::string& path, const std::istream& content)
+  void Write(const std::string& path, std::istream& content)
   {
   }
 
   void Move(const std::string& fromPath, const std::string& toPath)
   {
   }
 
   void Remove(const std::string& path)
   {
   }
@@ skipping 45 matching lines @@
   virtual void SetUp()
   {
     jsEngine = CreateJsEngine();
     jsEngine->SetLogSystem(AdblockPlus::LogSystemPtr(new ThrowingLogSystem));
     jsEngine->SetFileSystem(AdblockPlus::FileSystemPtr(new ThrowingFileSystem));
     jsEngine->SetWebRequest(AdblockPlus::WebRequestPtr(new ThrowingWebRequest));
   }
 };
 
 #endif