This fixes a regression in 3041480600
that would cause anything rendered on the backend differently than on
the frontend to experience this animation.
We actually only want to do the animation when the message content was
changed in a way that generates an edit history event, i.e. a
user-facing edit, not in cases where we're either transparently
swapping in post-backend-rendering content (e.g. with link previews)
or cases where there's a discrepancy between the exact HTML from the
frontend and backend markdown processes (e.g. mentions).
This is mostly just moving methods out of compose.js.
The variable `is_composing_message`, which isn't a boolean, has
been renamed to `message_type`, and there are new functions
set_message_type() and get_message_type() that wrap it.
This commit removes some shims related to the global variable
`compose_state`; now, `compose_state` is a typical global
variable with a 1:1 relationship with the module by the same
name.
The new module has 100% line coverage, most of it coming
via the tests on compose_actions.js. (The methods here are
super simple, so it's a good thing that the tests are somewhat
integrated with a higher layer.)
Tim Abbott
Steve Howell