com.unity.timeline 1.4.0 Package Notes

Added `ClipCaps.AutoScale` to automatically change the speed multiplier value when the clip is trimmed in the Timeline window.
Added a `DeleteClip` method in `TrackAsset`.
Added dependency on Animation, Audio, Director and Particle System modules. (1229825)
Added an option in `TimelineAsset.EditorSettings` to disable scene preview.
Added base classes to define custom actions:
- `TimelineAction`
- `TrackAction`
- `ClipAction`
- `MarkerAction`
Added the following attributes that can be used with action classes:
- `ApplyDefaultUndo` to automatically manage undo operations.
- `ActiveInMode` to control in which Timeline mode the action is valid.
- `MenuEntry` to add the action to the context menu.
- `TimelineShortcut` can be added to a static method to invoke the action with a shortcut.
`Invoker` to invoke actions using Timeline's selection or context.
`MenuOrder` contains menu priority values, to be used with `MenuEntry`.
`TimelineModes` to specify in which mode an action is valid, to be used with `MenuEntry`.
`ActionContext` to provide a context to invoke `TimelineAction`s.
`ActionValidity` to specify is an action is valid for a given context.
`UndoExtension` to manage undo operations with common Timeline types.

Improved performance with ControlTracks in preview mode for cases where multiple Control Tracks are assigned to the same PlayableDirector.
Improved layout and appearance of track header buttons.
Reduced icons' file size without any quality loss.
A track's binding will be duplicated when pasting or duplicating a track.
When creating a new timeline asset, the "Timeline" suffix will not be added to the file name twice.
`ClipCaps.All` now includes the new `Autoscale` feature. To get the previous `ClipCaps.All` behaviour on clips, use
```
ClipCaps.Looping | ClipCaps.Extrapolation | ClipCaps.ClipIn | ClipCaps.SpeedMultiplier | ClipCaps.Blending
```
Inline curve selection is now synced with the clip's selection.
Selecting a curve view property will also select the corresponding curve view.
Clicking and holding the `Command` or `Control` key on a curve view will deselect it if it was already selected.
Improved Timeline window UI performance.

Selecting clips from locked tracks is not allowed anymore when using the playhead's context menu.
Inserting gaps in locked tracks is not allowed anymore.
When adding an Activation track, the viewport is adjusted to show the new Activation clip.
Fixed issue where trimming AnimationClips would also change the speed multiplier.

com.unity.timeline 1.4.0