First cut at the landing page.
Missing debugger walk thru.

BUG=None
TEST=None
R=sbc@chromium.org, binji@chromium.org

Review URL: https://codereview.chromium.org/345703002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@278510 0039d316-1c4b-4281-b951-d872f2087c98