AppListItem title -> short_name, full_name -> name

Make Extension.name and Extension.short_name map directly to AppListItem.name AppListItem.short_name (instead of full_name and title).

Also, sync the full name for ExtensionAppItem, but do not override the name set by the Extension since we do not sync the short name.

BUG=344950

For ash/shell/app_list.cc:

R=jennyz@chromium.org, tapted@chromium.org, xiyuan@chromium.org
TBR=jamescook@chromium.org

Review URL: https://codereview.chromium.org/171713003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252605 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252605