Added initial interface hooks betweek WebKit code and renderer-side worker code.
The proper messages are generated to fire off a shared worker, but they are currently
ignored by the browser process.

BUG=26233
TEST=none (will enable layout tests when basic functionality available)

Review URL: http://codereview.chromium.org/340036

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@30599 0039d316-1c4b-4281-b951-d872f2087c98