Remove permission warnings from most tabs and windows APIs.

chrome/test/data/extensions/api_test/all_urls/content_script/manifest.json

 {
    "background": {
      "scripts": ["background.js"]
    },
    "content_scripts": [ {
       "js": [ "content_script.js" ],
       "matches": [ "<all_urls>" ]
    } ],
+   "permissions": [ "tabs" ],
    "description": "Test whether whitelisted extensions can run scripts everywhere using content script",
    "name": "AllUrls content script permissions",
    "manifest_version": 2,
    "version": "1.0"
 }