various ux tweaks
Merge branch 'master' into ux-tweaks
Remove an 1px border of tab label
review comments
Merge pull request #237 from dart-lang/ux-tweaks

various ux tweaks
Merge pull request #241 from ikarienator/EditorLayer2

Removes an 1px border of tab label
Remove dirty flag changed event as it`s not used
Merge pull request #242 from ikarienator/EditorLayer3

Remove dirty flag changed event as it's not used.