Issue 4931 - add possibility to not send data depending on connection properties

include/AdblockPlus/JsEngine.h

Index: include/AdblockPlus/JsEngine.h
diff --git a/include/AdblockPlus/JsEngine.h b/include/AdblockPlus/JsEngine.h
index 3f43388620da169d6b457b4e8ef35caaadea1605..02981488444a28021431447a13b3b79e6fa098c8 100644
--- a/include/AdblockPlus/JsEngine.h
+++ b/include/AdblockPlus/JsEngine.h
@@ -23,6 +23,7 @@
 #include <stdexcept>
 #include <stdint.h>
 #include <string>
+#include <mutex>
 #include <AdblockPlus/AppInfo.h>
 #include <AdblockPlus/LogSystem.h>
 #include <AdblockPlus/FileSystem.h>
@@ -88,6 +89,12 @@ namespace AdblockPlus
     typedef std::function<void(JsValueList& params)> EventCallback;
 
     /**
+    * Callback function returning false when current connection is not allowed
+    * e.g. because it is a metered connection.
+    */
+    typedef std::function<bool()> IsConnectionAllowedCallback;
+
+    /**
      * Maps events to callback functions.
      */
     typedef std::map<std::string, EventCallback> EventMap;
@@ -222,6 +229,19 @@ namespace AdblockPlus
     void SetWebRequest(WebRequestPtr val);
 
     /**
+    * Registers the callback function to check whether current connection is
+    * allowed for network requests.
+    * @param callback callback function.
+    */
+    void SetIsConnectionAllowedCallback(const IsConnectionAllowedCallback& callback);
+
+    /**
+     * Checks whether current connection is allowed. If
+     * IsConnectionAllowedCallback is not set then then it returns true.
+     */
+    bool IsConnectionAllowed();
+
+    /**
      * @see `SetLogSystem()`.
      */
     LogSystemPtr GetLogSystem();
@@ -264,6 +284,8 @@ namespace AdblockPlus
     LogSystemPtr logSystem;
     std::unique_ptr<v8::Persistent<v8::Context>> context;
     EventMap eventCallbacks;
+    std::mutex isConnectionAllowedMutex;
+    IsConnectionAllowedCallback isConnectionAllowed;
   };
 }