Issue #4692 - Rewrite `SetTimeout` facility to avoid `JsValuePtr` and `JsValueList`

src/V8Upgrade.h

+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-2016 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
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/**
+ *  \file V8Upgrade Facilities to ease the upgrade from old versions of v8
+ */
+
+#if !defined(V8_UPGRADE_H)
+#define V8_UPGRADE_H
+
+#include <v8.h>
+
+/**
+ * Mimic for the next-generation version of v8::Persistent
+ *
+ * Recent versions of v8 significantly improve the usability of v8::Persistent.
+ * This class provides an interface that mimics the new version.
+ * An upgraded version of v8::Peristent should drop in and replace this class
+ *   with no changes to code other than the type declaration.
+ *
+ * Features present in new versions of v8::Persistent that are present here:
+ * - Objects follow conventional C++ scope behavior.
+ *   Dispose() is no longer present; its equivalent is called in the destructor.
+ * - Get() is a convenience method to convert to a Local<T>
+ * - A copy constructor.
+ */
+template<class T>
+class V8PersistentNG
+{
+  /**
+   * The underlying Persistent
+   */
+  v8::Persistent<T> persistent;
+  /**
+   * Isolate pointer from which this Persistent was constructed.
+   * This is needed for the copy constructor using the old Persistent class.
+   */
+  v8::Isolate* isolate;
+
+public:
+  V8PersistentNG() // = default;
+  {}
+
+  template<class S>
+  V8PersistentNG(v8::Isolate* isolate, v8::Local<S> that)
+    : persistent(isolate, that),
+    isolate(isolate)
+  {}
+
+  ~V8PersistentNG()
+  {
+    persistent.Dispose();
+  }
+
+  /**
+   * Copy constructor
+   */
+  V8PersistentNG(const V8PersistentNG<T>& that)
+    : isolate(that.isolate)
+  {
+    persistent.Reset(that.isolate, that.persistent);
+  }
+  /**
+   * Move constructor
+   */
+  V8PersistentNG(V8PersistentNG<T>&& that)
+    : isolate(that.isolate)
+  {
+    persistent.Reset(that.isolate, that.persistent);
+  }
+  /**
+   * Copy assignment
+   */
+  V8PersistentNG& operator=(const V8PersistentNG<T>& that)
+  {
+    isolate = that.isolate;
+    persistent.Reset(that.isolate, that.persistent);
+    return *this;
+  }
+  /**
+   * Move assignment
+   */
+  V8PersistentNG& operator=(V8PersistentNG<T>&& that)
+  {
+    isolate = that.isolate;
+    persistent.Reset(that.isolate, that.persistent);
+    return *this;
+  }
+
+  /**
+   * Create a Local from this Persistent.
+   *
+   * The function signature matches that of the new v8.
+   * The `isolate` argument seems redundant, but that's out of our hands.
+   */
+  v8::Local<T> Get(v8::Isolate* isolate) const
+  {
+    return v8::Local<T>::New(isolate, persistent);
+  }
+};
+
+#endif