After this patch, we can execute Dart code and draw the result via MGL. We
still need to plumb in services.

Wire sky_shell.mojo up to native_viewport

After this patch, we can execute Dart code an create an X window. There's a
sketch of some graphics code, but it's not wired up yet.

Rev packages again and this time update the mojo_sdk dependency

Make Xcode run `pub get` automatically

Bump sky_engine and sky_services package versions

Roll dart 3

Move GPU code into direct

I'll add another subdirectory to GPU for Mojo soon.

Provide a handle for the ServiceProvider stub used by the application…

Provide a handle for the ServiceProvider stub used by the application to expose services to the embedder

Update the path for dart:ui_internals

Do not delete the DrainJob within the DrainJob::Start callback

Include raw_keyboard.mojom in the Linux build too.

Nuke //ui/events, all users are runtime dead

DrainDataPipeInBackground posts a callback to DrainJob::Start, which
constructs a DataPipeDrainer.  The DataPipeDrainer's constructor may
call OnDataComplete.  If this happens, it is unsafe to delete the
DrainJob while the callback is still running.

Add a basic sky_shell.mojo

Make the user specify the path to the flutter repo in Xcode

Currently sky_shell.mojo can't load any Flutter apps or draw to the screen, but
that will come in later patches.

Move platform-specific code for sky/shell into sky/shell/platform

This patch prepares us to add support for Mozart.

The dart_pkg rule for sky_engine now preserves directory structure. Account for the same in SnapshotterInvoke

Fix sky_build.py