Update CHANGELOG.md
Update the webui dartium extension

Review URL: https://chromiumcodereview.appspot.com//12221076
fix #318 - use web-ui-dev@dartlang.org list

This new list is for discussing development of web-ui
add a note about the web-ui-dev list
add web-ui-dev to code review settings

Review URL: https://chromiumcodereview.appspot.com//12213096
Several changes to component_build

Review URL: https://chromiumcodereview.appspot.com//12220088
merged with master