This change enables attaching images to the style with batches and
avoids massive re-allocations. Thus, it improves UI performance
especially at start-up time.
- Do not carry it over everywhere as parameter, it is a shared
instance anyway and the lifecycle is pretty much the app lifecycle
from the moment we instantiate a map.
- Rename to BackgroundScheduler because it is a Scheduler that will
do tasks in the background, we don't make assumptions if it is a
thread pool or a single thread.
- Most importantly, remove the dependency from `core` on `platform`.
Before this change, ImageManger's 'done' callback for onStyleImageMissing observer
notification that was created on renderer thread, could be called from different thread,
therefore, is not thread safe. For example, on Android platform, callback was invoked
from UI thread. This change makes callback to be scheduled on originating thread.
`LayerManager` is now responsible for `RenderLayer` instances creation,
so that there is a single entry point for creating of objects, which
correspond to a certain layer type.
The `LayerType type` field is dropped from `Layer::Impl`.
Port of https://github.com/mapbox/mapbox-gl-js/pull/5101: adds a new render pass `Pass3D` before any other rendering wherein we render layers with 3D passes (fill-extrusion layers) to offscreen framebuffers, sharing a depth renderbuffer between those layers in order to render 3D space correctly. Those framebuffers are saved on the RenderLayers and copied back to the map during the translucent pass. Rendering to offscreen framebuffers before we do any clear + draw means we can avoid expensive framebuffer restores.
- Guards against duplicate activations by checking wether the backend of the prior scope is the same as the current ones
- Makes sure that only the most outer backend scope deactivates by tracking activation state
* Eliminates the need for EnableImmutableFromThis
* Eliminates the dependency of {Source,Layer}::Impl on corresponding Render class (circular dependency)
