Issue #3593, #1197- fix isolate management

include/AdblockPlus/JsEngine.h

Index: include/AdblockPlus/JsEngine.h
diff --git a/include/AdblockPlus/JsEngine.h b/include/AdblockPlus/JsEngine.h
index 2893752f6738d6d585a0b75c65d67d759d513b92..7ddbeb0f69b0253123767dd31c218b5c0f8c68c4 100644
--- a/include/AdblockPlus/JsEngine.h
+++ b/include/AdblockPlus/JsEngine.h
@@ -48,6 +48,28 @@ namespace AdblockPlus
    */
   typedef std::shared_ptr<JsEngine> JsEnginePtr;
 
+  /**
+   * Scope based isolate manager. Creates a new isolate instance on
+   * constructing and disposes it on destructing.
+   */
+  class ScopedV8Isolate
+  {
+  public:
+    ScopedV8Isolate();
+    ~ScopedV8Isolate();
+    v8::Isolate* GetIsolate()
+    {
+      return isolate;
+    }
+  protected:
+    v8::Isolate* isolate;
+  };
+
+  /**
+   * Shared smart pointer to ScopedV8Isolate instance;
+   */
+  typedef std::shared_ptr<ScopedV8Isolate> ScopedV8IsolatePtr;
+
   /**
    * JavaScript engine used by `FilterEngine`, wraps v8.
    */
@@ -72,7 +94,7 @@ namespace AdblockPlus
      * @param appInfo Information about the app.
      * @return New `JsEngine` instance.
      */
-    static JsEnginePtr New(const AppInfo& appInfo = AppInfo());
+    static JsEnginePtr New(const AppInfo& appInfo = AppInfo(), const ScopedV8IsolatePtr& isolate = ScopedV8IsolatePtr());
 
     /**
      * Registers the callback function for an event.
@@ -215,13 +237,24 @@ namespace AdblockPlus
      */
     void SetGlobalProperty(const std::string& name, AdblockPlus::JsValuePtr value);
 
+    /**
+     * Returns a pointer to associated v8::Isolate.
+     */
+    v8::Isolate* GetIsolate()
+    {
+      return isolate->GetIsolate();
+    }
+
   private:
-    JsEngine();
+    explicit JsEngine(const ScopedV8IsolatePtr& isolate);
+
+    /// Isolate must be disposed only after disposing of all objects which are
+    /// using it.
+    ScopedV8IsolatePtr isolate;
 
     FileSystemPtr fileSystem;
     WebRequestPtr webRequest;
     LogSystemPtr logSystem;
-    v8::Isolate* isolate;
     std::unique_ptr<v8::Persistent<v8::Context>> context;
     EventMap eventCallbacks;
     JsValuePtr globalJsObject;