Added App Launcher icons suitable for use on Linux.

The new icons are PNG versions of the images in win/app_list.ico.

BUG=299250
R=oshima@chromium.org

Review URL: https://codereview.chromium.org/131743010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245854 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245854