1. Visit netflix, log in and start some movie. 
2. Close netflix tab
3. Remove Cookies, Cache and Media Licenses for All Time.

All data should be removed but the database in "File System/Plugins/Origins" still contains a key containing "netflix.com". There is another leveldb instance in "File System/Plugins/000/application_x-ppapi-widevine-cdm/Paths" and some "random" files in File "System/Plugins/000/application_x-ppapi-widevine-cdm/00".


lev "File System/Plugins/Origins"
/>ls
LAST_PATH                       ORIGIN:https_www.netflix.com_0  
/>get LAST_PATH
'000'
/>get ORIGIN:https_www.netflix.com_0 
'000'
/>

jrummel@: Do you know what these are for?

Looks like this is the same as issue 823071, specifically the filesystem API case. This particular directory is c/o PluginPrivateFileSystemBackend but like the other FileSystem API back-ends it maintains metadata (origin/directory mapping, etc) in a common leveldb instance.

After discussing with jsbell@, he says the options appear to be:
1) Media Licenses could stop using FileSystem (use this bug)
2) or we fix FileSystem (issue 823071)

Tentatively dupe'ing against issue 823071 for now, but if jrummell@ thinks Media Licenses can be moved off FileSystem then please un-dupe and take it.

Media Licenses are stored in the plugin file system for backwards compatibility (as encrypted playback used to be a ppapi plugin). We still need the ability to read and write the files, so I assume the file system will still continue to be used.

Unfortunately leveldb can't ever really guarentee that your keys will no longer exist on disk. The primary problem is the lazy compaction, which happens intermittently so keys&values won't be deleted right away (only actually deletes from disk on compaction). Second, there is a chance that your key will be used for an upper or lower bound of the 'range' on a level file, which could persist it until that level file is rewritten, which could never happen.

What do we really want here? It is absolutely necessary to remove all traces of data off of the local disk? Do we care about keys by themselves, or just the values?

I'm not sure if this is just a duplicate of issue 823071. 
"File System/Plugins/Origins" still contained some actual data when I opened the database after deleting all cookies and media licenses. This is not just garbage that will might get removed by compaction later.