First implementation of drag to treeview
Merge remote-tracking branch 'upstream/master' into 130-drag-to-import
Removed fullPath since it's not useful.
Reverted test code. Added TODO.
Alphabetize CSS
Use interpolation
Introduced cancelEvent(). Use template for TreeViewCell. Cleaning template for FileItemCell. Moved widget CSS files to lib/ui/widgets.
Merge
Fixed merge with master
Merge pull request #217 from dinhviethoa/130-drag-to-import

Drag to TreeView.
Minor impromevents in comments etc.; no behavior changes
Merge pull request #231 from ussuri/spark-splitter

Minor impromevents in comments etc.; no behavior changes
disable ace syntax analysis
add line comment
Merge pull request #232 from dart-lang/ace-tweak

Ace tweak
Implemented TreeView selection setter (fixed #235)
Merge pull request #236 from dinhviethoa/235-treeview-selection

Implemented TreeView selection setter (fixed #235)
resolve merge
merge master