Tells the dialog to show itself. Those overriding can call this._super() to get a deferred object created for them.
A promise that is resolved when the dialog is submitted,
or rejected if it's cancelled. Returned object structure when resolved:
fileName [type: String] - The name of the file being saved.
parentFileSystemEntry [type: dundas.filesystem.FileSystemEntry] - The parent folder to save the file to.
overwrite [type: Boolean] - Indicates if an existing file with the same name is being overwritten.
fileType [type: String] - The name of the selected file type.
quotaInformation [type: Object, optional: true] - (optional) The quota information for the object type being saved, or false if quota checking is not applicable. Structure:
quotaAlreadyReached [type: Boolean] - Indicates if the quota has already been reached.
signalToShow [type: String, optional: true] - (optional) The localized message to show regarding quota status.