Treat files downloaded from the address bar as "always safe" (including extensions per discussion...

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 5204 matching lines @@
         "description": "Fired when a navigation is committed. The document (and the resources it refers to, such as images and subframes) might still be downloading, but at least part of the document has been received from the server and the browser has decided to switch to the new document.",
         "parameters": [
           {
             "type": "object",
             "name": "details",
             "properties": {
               "tabId": {"type": "integer", "description": "The ID of the tab in which the navigation occurs."},
               "url": {"type": "string"},
               "frameId": {"type": "integer", "description": "0 indicates the navigation happens in the tab content window; a positive value indicates navigation in a subframe. Frame IDs are unique within a tab."},
               "transitionType": {"type": "string", "enum": ["link", "typed", "auto_bookmark", "auto_subframe", "manual_subframe", "generated", "start_page", "form_submit", "reload", "keyword", "keyword_generated"], "description": "Cause of the navigation. The same transition types as defined in the history API are used."},
-              "transitionQualifiers": {"type": "array", "description": "A list of transition qualifiers.", "items:": {"type": "string", "enum": ["client_redirect", "server_redirect", "forward_back"]}},
+              "transitionQualifiers": {"type": "array", "description": "A list of transition qualifiers.", "items:": {"type": "string", "enum": ["client_redirect", "server_redirect", "forward_back", "from_address_bar"]}},
               "timeStamp": {"type": "number", "description": "The time when the navigation was committed, in milliseconds since the epoch."}
             }
           }
         ]
       },
       {
         "name": "onDOMContentLoaded",
         "type": "function",
         "description": "Fired when the page's DOM is fully constructed, but the referenced resources may not finish loading.",
         "parameters": [
@@ skipping 3085 matching lines @@
             "type": "function",
             "description": "Called when the browser's passwords have been cleared.",
             "optional": true,
             "parameters": []
           }
         ]
       }
     ]
   }
 ]