Called when a page should show a permission prompt. |prompt_id| uniquely identifies the prompt. |requesting_origin| is the URL origin requesting permission. |requested_permissions| is a combination of values from cef_permission_request_types_t that represent the requested permissions. Return true (1) and call cef_permission_prompt_callback_t::Continue either in this function or at a later time to continue or cancel the request. Return false (0) to proceed with default handling. With the Chrome runtime, default handling will display the permission prompt UI. With the Alloy runtime, default handling is CEF_PERMISSION_RESULT_IGNORE.