switched to spark_dart
Revert "switched to spark_dart"

This reverts commit b4744b51630160e288046f0439efb3f249105b88.
Merge branch 'master' of https://github.com/dart-lang/spark
expander icon tweaks
Merge branch 'master' of https://github.com/dart-lang/spark
Half-way through: dumb UI works, but underlying Dart is mostly disabled

...as a result, the toolbar and splitter show, but buttons don't do anything, and file treeview pane and edit pane are empty.
implement rename
Merge branch 'master' into work2
working on double-click toggle
more tweaks
fix warnings
Widgets: cleanups, fixes, improvements
Make splitview visible again + toolbar style + move images

Some problems still remain: the hotdog menu button's image is still misaligned, the hotdob menu itself has wrong margins.
Fix the layout after a recent breaking change in polymer-flex-panel
rename toggleExpanded() to toggleNodeExpanded()
Merge pull request #357 from dart-lang/treeview_tweaks

Treeview tweaks
whitespace only changes
Merge pull request #363 from dart-lang/ws_cleanup

whitespace only changes
removed open file after rename
Merge pull request #358 from dart-lang/rename

implement rename