Add origin permissions to the extension permissions API.

chrome/common/extensions/api/extension_api.json

 [
   {
     "namespace": "extension",
     "unprivileged": true,
     "types": [
       {
         "id": "MessageSender",
         "type": "object",
         "description": "An object containing information about the script context that sent a message or request.",
         "properties": {
@@ skipping 1053 matching lines @@
     "types": [
       {
         "id": "Permissions",
         "type": "object",
         "properties": {
           "permissions": {
             "type": "array",
             "items": {"type": "string"},
             "optional": true,
             "description": "List of named permissions (does not include hosts or origins)."
+          },
+          "origins": {
+            "type": "array",
+            "items": {"type": "string"},
+            "optional": true,
+            "description": "List of origin permissions."
           }
         }
       }
     ],
     "events": [
       {
         "name": "onAdded",
         "type": "function",
         "unprivileged": true,
         "description": "Fired when the extension acquires new permissions.",
@@ skipping 6308 matching lines @@
                 "description": "A string result code. The value is non-empty on success only in tests.",
                 "optional": "true"
               }
             ]
           }
         ]
       }
     ]
   }
 ]