There were some changes that were lost/added by mistake
during a rebase of #17707 after #18154 was merged.
Fixes the GIF icon being hidden / displayed incorrectly
with respect to the settings.
These changes were originally part of
67527a2517 but
were lost during the rebase.
setTimeout doesn't work all the time especially when trying to
hide and display the popover at once, like when you press
to open giphy popover in message edit form while another giphy
popover is open from the compose box.
MutationObserver works reliably, hence we choose to use it
instead.
We convert the following elements to use a class instead of
id for accessing them across the codebase:
* markdown_preview
* undo_markdown_preview
* markdown_preview_spinner
* message_edit_content
* preview_content
Converted them together since changes to one impacted the other in
some modules like click_handlers.
Also, added a function in rows to get `message_row`.
We use GIPHY web SDK to create popover containing GIFs in a
grid format. Simply clicking on the GIFs will insert the GIF in the compose
box.
We add GIPHY logo to compose box action icons which opens the GIPHY
picker popover containing GIFs with "Powered by GIPHY"
attribution.