If GPURasterizer::NotifyNextFrameOnce was rapidly invoked twice could
have lead to a null pointer exception.
Also ftp::WeakPtr are not thread safe and should not be dereferenced
from other threads.
* Add back launch screen view until first frame on iOS
* improvements
* Move callback plumbing from ios surfaces to the gpu rasterizer. Didn’t wire java JNI yet.
* Android JNI
* Fix ios reference count and let android engine manage a view on top with launch screen
* Hook up Android activity and view
* review notes
* review notes
* Move thread switching upstream. Use weak references for callbacks.
* Some clean up
The GPUSurfaceGL holds references to Skia objects that may own GL objects.
If the GL objects are destructed on the GPU thread after the EGL context has been
dropped, then the GL delete calls will not take effect.
We push a bit up the tree during preroll to learn whether there system
composited layers below each layer. During update scene, we squash down
to paint tasks, which we execute after publishing the new scene.
* Namespaces have been updated to reflect the move from //flutter/sky/shell to //flutter/shell.
* shell/BUILD.gn file has been split into smaller GN files for each subcomponent of the shell (common, GPU, diagnostic, testing).
* GN dependencies have been rewritten to stop exposing common shell dependencies as public. Duplicates have also been removed.
* GPU subcomponent has been updated make it more suitable for Vulkan integration.
* The GLFW backend has been resurrected.
