Rework API reference pages
(this is a fresh copy of https://codereview.chromium.org/121713002/ with correct BaseURL)

BUG=340702
NOTRY=true

Review URL: https://codereview.chromium.org/149673004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251240 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251240