Updating the doc to reflect the new experimental.keybinding API.

Adding missing elements from previous API updates (someone forgot to run build.py).

Tiny code-change in extension.cc which was suggested during review, but I forgot to do.

BUG=27702
TEST=None (doc change)
Review URL: https://chromiumcodereview.appspot.com/9465005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@123724 0039d316-1c4b-4281-b951-d872f2087c98
6 files changed