* FIX: Cache missing inline oneboxes
Some inline oneboxes were not cached when the server did not return an
answer for an URL and the queried URL and the absolute URL were
different.
For example, if user typed www.example.com, the client asked the server
for http://www.example.com and if the server returned an empty response,
then the client would keep requesting an inline onebox everytime the
composer changed.
In other words, the key used for reading (the absolute URL) and the one
used for writing (the URL as typed by the user) were not the same when
the server returned an empty response.
* DEV: Check cache before making request
There is another cache check in PrettyText, but that is not enough if
multiple requests are pending. This problem was made obvious in tests,
but can happen for users with slow connections.
There were two constants here, `INLINE_ONEBOX_LOADING_CSS_CLASS` and
`INLINE_ONEBOX_CSS_CLASS` that were both longer than the strings they
were DRYing up: `inline-onebox-loading` and `inline-onebox`
I normally appreciate constants, but in this case it meant that we had
a lot of JS imports resulting in many more lines of code (and CPU cycles
spent figuring them out.)
It also meant we had an `.erb` file and had to invoke Ruby to create the
JS file, which meant the app was harder to port to Ember CLI.
I removed the constants. It's less DRY but faster and simpler, and
arguably the loss of DRYness is not significant as you can still search
for the `inline-onebox-loading` and `inline-onebox` strings easily if
you are refactoring.
