Lots of code cleanup.

Cleanup runtime.dart.

Fixes to ChromeCompleter.

Comment out test chrome.app.window.minimize test that is not completing on
my system.

Other cleanup related to changes to runtime.dart and chromecompleter.
Uncomment lines that I accidentally left commented out.
Merge branch 'runtime'
Edits in response to pull request comments.
Merge pull request #64 from DrMarcII/master

Fixes to (primarily) runtime.dart.