Porting changes on DevSite back to Chromium:

RST-ifying new landing page. Adding needed CSS. Renaming the original
index.html to sitemap.html.

R=binji@chromium.org

Review URL: https://codereview.chromium.org/113133015

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243123 0039d316-1c4b-4281-b951-d872f2087c98
Turn on context menu tests

The test harness flakiness was fixed with 115473002 and 114563002.  Turning these back on

BUG=326769
NOTRY=true

Review URL: https://codereview.chromium.org/106053009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243124 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243123
SVN changes up to revision 243124