Remove support for "mojo:" libraries
Remove support for "mojo:" libraries

We ended up using "dart:" instead. This change shouldn't have any observable
effects.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1192743011.

afandria/mojo,chinmaygarde/mojo,afandria/mojo,chinmaygarde/mojo,jianglu/mojo,chinmaygarde/mojo,afandria/mojo,jianglu/mojo,jianglu/mojo,chinmaygarde/mojo,jianglu/mojo,chinmaygarde/mojo,afandria/mojo,chinmaygarde/mojo,afandria/mojo,jianglu/mojo,chinmaygarde/mojo,afandria/mojo,afandria/mojo,jianglu/mojo,jianglu/mojo,chinmaygarde/mojo,chinmaygarde/mojo,jianglu/mojo,afandria/mojo