giphy: Use MutationObserver to check when popover is visible.
giphy: Use MutationObserver to check when popover is visible.

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.

eeshangarg/zulip,rht/zulip,kou/zulip,eeshangarg/zulip,rht/zulip,hackerkid/zulip,zulip/zulip,punchagan/zulip,punchagan/zulip,hackerkid/zulip,eeshangarg/zulip,rht/zulip,hackerkid/zulip,zulip/zulip,rht/zulip,eeshangarg/zulip,rht/zulip,andersk/zulip,zulip/zulip,kou/zulip,andersk/zulip,andersk/zulip,hackerkid/zulip,andersk/zulip,hackerkid/zulip,eeshangarg/zulip,andersk/zulip,kou/zulip,punchagan/zulip,kou/zulip,rht/zulip,andersk/zulip,hackerkid/zulip,kou/zulip,kou/zulip,punchagan/zulip,punchagan/zulip,zulip/zulip,zulip/zulip,punchagan/zulip,rht/zulip,zulip/zulip,kou/zulip,eeshangarg/zulip,zulip/zulip,eeshangarg/zulip,hackerkid/zulip,andersk/zulip,punchagan/zulip