Enable run spark in spark.
Logic to switch between two spark ids.
cleanup
remove empty lines.
nits.
Move JsonPrinter to util class.
Only switch manifest keys, if spark is run.
fix indent
remove empty line.
Merge pull request #2100 from dart-lang/spark_run

Launch spark from spark
nits
Merge pull request #2112 from devoncarew/devoncarew_nits2

nits
Merge branch 'master' into devoncarew_launch_refactor
more refactoring