* Add support for save/replay of the current view.
* Add support for having distinct draw/read surfaces.
Adds support to egl & glx drivers for distring draw/read surfaces and
uses this support to implement mirrorFrame using a single blit.
* Use src/dst, Viewport, clean up apis.
* Add SwapChain READABLE Config.
* Commit & setPresentationTime optional on mirror.
* Fix flag check.
* Add documentation for READABLE swap chain config.
* Fix missed s/ExternalContext/Platform/ cases.
* Build break fix.