estimatedSize
Returns the estimated total size of the media, which includes all assets such video, audio and subtitles.
The actual size of the media that will be used by the host device may vary based on the partition type and format of the storage. This method requires the Media Manifest to estimate the size, therefore it might download the manifest and store it to the directory provided in the ( object in the constructor, if it has not been done already.
Parameters
callback
the approximate size of the media.