This feature is intended for spot. Spot can have an
HDMI -> usb adapter hooked up to it. In that case,
attempting to screenshare should use that adapter
as a screensharing source. Jitsi-Meet should pass
a configured screenshare source into lib-jitsi-meet
so it can be used as a source.

We no longer need it since Rect 16 takes care of passing the context around.
It's also deprecated: https://atlaskit.atlassian.com/packages/core/layer-manager

componentWillMount is a deprecated lifecycle method;
componentDidMount should be used to kick off things
like ajax. In the case of the _App hierarchy, a promise
chain is used to perform initialization, and it is
first started in the constructor by initializing
storage. However, by the time storage is initialized,
resolving the first promise, _App has already mounted.
So, move it all to the componentDidMount lifecycle.

The package now requires using a ModalTransition component
to handle animations. The existing DialogContainer component
has been split into native and web implementations to support
this change.

Updating react-native-fast-image brings a couple of interesting changes:

- onLoad is not called for cached images (reported and ignored upstream)
- load progress not working if component not displayed (on Android)

In order to fix this, a combination of 2 approaches was used:

- onLoadEnd / onError are used to detect if the image is loaded
- off-screen rendering is used on Android to get progress events

While implementing the above, yours truly noticed the complexity was increasing
way too much, so some extra refactoring was also performed:

- componentWillReceiveProps is dropped
- an auxiliary component (AvatarContent) is used for the actual content of the
  Avatar, with the former passing the key prop to the latter

Using the key prop ensures AvatarContent will be recreated if the URI changes,
which is not a bad idea anyway, since the new image needs to be downloaded.

The upstream package has been unmaintained for 2 years now, and making the litle
changes needed as React Native needs them is getting old. The actual
funcionality is a couple of one-liners plus tons of boliterplate, which gets
reduced by quite a bit if we just embed it. So here it goes.

It doesn't seem like videoTrack needs to be set onto state
if it can be accessed directly from props. Removing the state
automatically removes the deprecated componentWillReceiveProps.

Filmstrip remote thumbnails display under certain conditions, as
defined in filmstrip/functions.web.js. Previously the raw
participant count was used, which included fake participants.
Using the selector getParticipantCount excludes fake participants,
causing YouTube thumbnails to remain hidden in a 1-on-1 call.

- Derive the showOverlay state. When the sidebar should be hidden,
  the internal showOverlay state should remain true until the
  animation hides it. When the sidebar should show, the showOverlay
  state should become true immediately.
- Use PureComponent to prevent additional animation triggers
  instead of explicitly checking changes to the "show" prop.

Based on react-native docs, looks like animations should be
started after mount. Updating animation states I'm not certain
on so I moved it to componentDidUpdate and tested with the
live streaming label to ensure the component still animated fine.

For the most part the changes are taking the "static propTypes" declaration off
of components and declaring them as Flow types. Sometimes to support flow some
method signatures had to be added. There are some exceptions in which more had
to be done to tame the beast:
- AbstractVideoTrack: put in additional truthy checks for videoTrack.
- Video: add truthy checks for the _videoElement ref.
- shouldRenderVideoTrack function: Some component could pass null for the
  videoTrack argument and Flow wanted that called out explicitly.
- DisplayName: Add a truthy check for the input ref before acting on it.
- NumbersList: Move array checks inline for Flow to comprehend array methods
  could be called. Add type checks in the Object.entries loop as the value is
  assumed to be a mixed type by Flow.
- AbstractToolbarButton: add additional truthy check for passed in type.

* feat(welcome-page): Redesign.

* Style adjustments.

It was moved to js-utils, so make use of it.

- Change "features/chat" to support listening for new chat messages
  and storing them, removing that logic from conference.js.
- Combine chat.scss and side_toolbar_container.css, and remove unused
  scss files. Chat is the only side panel so the two concepts have
  been merged.
- Remove direct access to the chat feature from non-react and non-redux
  flows.
- Modify the i18n translate function to take in an options object.
  By default the option "wait" is set to true, but that causes
  components to mount after the parent has been notified of
  an update, which means autoscrolling down to the latest rendered
  messages does not work. With "wait" set to false, the children
  will mount and then the parent will trigger componentDidUpdate.
- Create react components for chat. Chat is the side panel
  plus the entiren chat feature. ChatInput is a child of Chat and
  is used for composing messages. ChatMessage displays one message
  and extends PureComponent to limit re-renders.
- Fix a bug where the toolbar was not showing automatically when
  chat is closed and a new message is received.
- Import react-transition-group to time the animation of the
  side panel showing/hiding and unmounting the Chat component.
  This gets around the issue of having to control autofocus if the
  component were always mounted and visibility toggled, but
  introduces not being able to store previous scroll state
  (without additional work or re-work).

There are (at least) two changes that are breaking:
- defaultTab is gone
- The re-rendering logic looks to have been re-written so that
  passing in a new array of tabs causes a re-render, which can
  reset the currently selected tab.

The fixes involved removing defaultTab from each tab configuration,
as it is no longer respected anyway. Also, instead of letting Tabs
be uncontrolled and allowing it to set its own selected, which
would result in the first tab automatically being selected on
Tabs re-render, use Tabs a controlled prop to dicate which
tab is selected; this is accomplished by specifying a selected
prop.

* feat(tile-view): initial implementation for mobile

- Create a tile view component for displaying thumbnails in a
  two-dimensional grid.
- Update the existing TileViewButton so it shows a label in the
  overflow menu.
- Modify conference so it can display TileView while hiding
  Filmstrip.
- Modify Thumbnail so its width/height can be set and to prevent
  pinning while in tile view mode.

* use style array for thumbnail styles

* change ternary to math.min for expressiveness

* use dimensiondetector

* pass explicit disableTint prop

* use makeAspectRatioAware instead of aspectRatio prop

* update docs

* fix docs again (fix laziest copy/paste job I've ever done)

* large-video: rename onPress prop to onClick

* change forEach to for...of

* use truthy check fallthrough logic instead of explicit if

* put tile view button second to last in menu

* move spacer to a constant

* the magical incantation to make flow shut up

Since they are a language feature, they make the source code more easily
comprehensible than `if (typeof XXX === 'undefined') { XXX = ...; }`.