Integrate camera easing into main render loop

[jfirebaugh]

Fixes #4670. Alternative to #5742.

[andy-mcdonald]

@jfirebaugh - Apologies for asking, but can you provide any timeline for when the next version (v0.42.3?) of mapbox-gl will be released? My team is working on a Mapbox-powered mobile web application (for a high profile client) that is due to launch on December 16th and we really need Markers to be stable.

I tried to run the build scripts from the master branch and manually patch them into the dist folder within the node module, but mapbox-gl.js is throwing an Uncaught Error: can't deserialize object of anonymous class and the map tiles are not displayed. Swapping in mapbox-gl-dev.js doesn't seem to have the new fix. Any ideas how I can get this working?

Again, sorry for pushing on this - I realize it's not practical to release a new version for every issue that gets resolved.

[bicubic]

I'm not 100% sure yet, but I think this change caused a regression where the map.transform updates lag by 1 frame behind the move event only during camera easing. I have an application that works fine on 0.34.0 but transforms are 1 frame late during easing on 0.43.0.

@mourner Can you please help me figure out where map.transform is being currently updated so I can investigate further?

[mourner]

@bicubic mostly in https://github.com/mapbox/mapbox-gl-js/blob/master/src/ui/camera.js, but also in some handler code like https://github.com/mapbox/mapbox-gl-js/blob/master/src/ui/handler/drag_pan.js#L126