* Remove most of mojo/dart/embedder
* Update roll.py to only import a subset of mojo/dart/embedder
* Add mojo/dart/observatory
* Update mojo_sdk_revision to get fixes to dart_pkg.py
This updates to mojo 4e4d51ce28a and mojo sdk 711a0bcfb141b4 and updates the sky
package's pubspec.yaml dependency to '>=0.1.0 <0.2.0' to be compatible with
the current mojo package. This includes an update to the Mojo Dart generator to
produce real classes for enums and the corresponding updates for users of the
KeyboardType enum in Sky as well as one scoped_ptr->std::unique_ptr in shell
corresponding to a change in the Mojo EDK.
When a new version of the sky and sky_services package are pushed this will fix
domokit/mojo#440.
This updates to mojo commit d259eb58aa59 and limits the roll script to
only pull in the parts of //mojo that are currently being used. More
stuff will be dropped in the future.
