After a message is saved asynchronsly, fire an event and pass the
message attributes to frontend listeners via the chrome-runtime API.
This behavior is similar to the 'storage' event fired by localStorage.
Getting up and running with IndexedDB was pretty easy, thanks to
backbone. The tricky part was making reads and writes asynchronous.
In that process I did some refactoring on Whisper.Threads, which
has been renamed Conversations for consistency with the view names.
This change also adds the unlimitedStorage permission.
Eliminates the global Whisper.Messages object and consolidates shared
send/receive logic in Whisper.Threads.
To the latter end, note that the decrypted array buffer on an attachment
pointer is now named data instead of decrypted, in order to match the
format of outgoing attachments presented by
FileReader.readAsArrayBuffers and let us use the same handler to base64
encode them.
Runtime reload is overkill and causes a jarring ux. Instead, send and
receive messages across the runtime. Also, if we need to jump between
the main ui and options pages, simply navigate within the current tab
rather than spawning a new one.
Firstly, don't initialize textsecure.nativclient unless the browser
supports it. The mimetype-check trick is hewn from nacl-common.js.
Secondly, nativeclient crypto functions will all automatically wait for
the module to load before sending messages, so we needn't register any
onload callbacks outside nativeclient.js. (Previously, if you wanted to
do crypto with native client, you would have to register a call back and
wait for the module to load.) Now that the native client crypto is
encapsulated behind a nice interface, it can handle all that
onload-callback jazz internally: if the module isn't loaded when you
call a nativeclient function, return a promise that waits for the load
callback, and eventually resolves with the result of the requested
command. This removes the need for textsecure.registerOnLoadCallback.
Finally, although native client has its quirks, it's significantly
faster than the alternative (emscripten compiled js), so this commit
also lets the crypto backend use native client opportunistically, if
it's available, falling back to js if not, which should make us
compatible with older versions of chrome and chromium.
