This commit prepares the frontend code to be consumed by webpack.
It is a hack: In theory, modules should be declaring and importing the
modules they depend on and the globals they expose directly.
However, that requires significant per-module work, which we don't
really want to block moving our toolchain to webpack on.
So we expose the modules by setting window.varName = varName; as
needed in the js files.
Here are the functions in top_left_corner:
get_global_filter_li: pure code move
update_count_in_dom: simplifed copy of similar function in stream_list.js
update_dom_with_unread_counts: pure code move, split out from function
of same name in stream_list.js
delselect_top_left_corner_items: pure code move
handle_narrow_activated: pure code move + rename
handle_narrow_deactivated: pure code move, split out from from function
of smae name in stream_list.js
Armaan Ahluwalia
Shubham Dhama
Shubham Padia
Steve Howell