Issue 5013 - Use const JsValue and pass reference where applicable

src/JsValue.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 155 matching lines @@
   v8::Local<v8::String> property = Utils::ToV8String(jsEngine->GetIsolate(), name);
   v8::Local<v8::Object> obj = v8::Local<v8::Object>::Cast(UnwrapValue());
   obj->Set(property, val);
 }
 
 v8::Local<v8::Value> AdblockPlus::JsValue::UnwrapValue() const
 {
   return v8::Local<v8::Value>::New(jsEngine->GetIsolate(), *value);
 }
 
+JsValue AdblockPlus::JsValue::Clone() const
+{
+  return JsValue(jsEngine, UnwrapValue());
+}
+
 void AdblockPlus::JsValue::SetProperty(const std::string& name, const std::string& val)
 {
   const JsContext context(jsEngine);
   SetProperty(name, Utils::ToV8String(jsEngine->GetIsolate(), val));
 }
 
 void AdblockPlus::JsValue::SetProperty(const std::string& name, int64_t val)
 {
   const JsContext context(jsEngine);
   SetProperty(name, v8::Number::New(jsEngine->GetIsolate(), val));
@@ skipping 57 matching lines @@
   const v8::TryCatch tryCatch;
   v8::Local<v8::Function> func = v8::Local<v8::Function>::Cast(UnwrapValue());
   v8::Local<v8::Value> result = func->Call(thisObj, args.size(),
     args.size() ? &args[0] : nullptr);
 
   if (tryCatch.HasCaught())
     throw JsError(tryCatch.Exception(), tryCatch.Message());
 
   return JsValue(jsEngine, result);
 }