am 438ca07b: Merge changes I66511c08,Ia051949f,Ic7451365,I5b571a4c into jb-mr2-dev

* commit '438ca07b6ba74235e87bfbd78c94874d8bbde391':
  Get rid of LayerBase.
  Make LayerDim a regular Layer instead of a LayerBase
  fold LayerBaseClient into LayerBase
  Remove support for ScreenshotLayer