Revises the concept of the media controller and workspace views (i.e. two central points of control) to be more granular. The main media object is now the `Frame`, which is a hybrid view and state machine.
The state machine is a collection of states, which are just generic instances of `Backbone.Model`. This circumvents the problem of juggling global parameters when changing states. Each state contains its own event loop. All events are also forwarded to the frame itself (as is the case in all model/collection relationships).
The frame view contains several regions, each of which can be overridden without harming or re-rendering the other regions. These work well when used in conjunction with the state machine events.
This removes the upload sidebar (don't worry, visible upload UI will return). Drag and drop uploading still works. The ability to upload has been abstracted into its own view (instead of being attached to the central workspace view).
Editing galleries is temporarily broken — the gallery creation and editing experiences will be unified in a future patch.
Adds events to detect dragging changes in `wp.Uploader` and adds methods to detect and leverage browser support for CSS3 transitions.
see #21390, #21809.
git-svn-id: https://develop.svn.wordpress.org/trunk@22320 602fd350-edb4-49c9-b593-d223f7449a82
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