Print to the browser console, works in fennec and desktop.

print_to_browser_console.cpp

#include "nsIConsoleService.h"

void someFunction() {
  uint32_t loadType = 25;

  nsCOMPtr<nsIConsoleService> consoleService = do_GetService(NS_CONSOLESERVICE_CONTRACTID);
  if (consoleService) {
     nsAutoCString message(nsPrintfCString("!!!!!!!!!!!!!!!!!!! LOAD TYPE %X", loadType));
    consoleService->LogStringMessage(NS_ConvertUTF8toUTF16(message).get());
  }
}