Move socket API from experimental to dev channel and remove some dead code

chrome/test/data/extensions/api_test/socket/api/manifest.json

 {
   "name": "chrome.socket",
   "version": "0.1",
   "manifest_version": 2,
-  "description": "end-to-end browser test for chrome.experimental.socket API",
+  "description": "end-to-end browser test for chrome.socket API",
   "app": {
     "background": {
       "scripts": ["background.js"]
     }
   },
   "permissions": [
-    "experimental",
     "socket"

[Peng, 2012/07/27 19:09:52]

I run browser test, no error happened. It because the old manifest file already
includes socket permission. 

[miket_OOO, 2012/07/27 19:21:24]

Great. Just for the sake of sanity, try removing the socket permission and
making sure that the test *does* fail. If not, then something's broken with the
permission framework. I'm slightly paranoid about this because it's the first
app API we've taken out of experimental, and I don't want anything to slip by
accidentally.

[Peng, 2012/07/27 19:31:42]

Done. Cases failed without socket permission.

   ]
 }