Implement initial chrome.browserAction.openPopup API.

chrome/common/extensions/api/browser_action.json

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 [
   {
     "namespace": "browserAction",
     "description": "Use browser actions to put icons in the main Google Chrome toolbar, to the right of the address bar. In addition to its <a href='#icon'>icon</a>, a browser action can also have a <a href='#tooltip'>tooltip</a>, a <a href='#badge'>badge</a>, and a <a href = '#popups'>popup</a>.",
     "types": [
       {
@@ skipping 292 matching lines @@
         "description": "Disables the browser action for a tab.",
         "parameters": [
           {
             "type": "integer",
             "optional": true,
             "name": "tabId",
             "minimum": 0,
             "description": "The id of the tab for which you want to modify the browser action."
           }
         ]
+      },
+      {
+        "name": "openPopup",
+        "type": "function",
+        "description": "Opens the extension popup window in the active window but does not grant tab permissions.",
+        "nodoc": true,
+        "parameters": [
+          {
+            "type": "function",
+            "name": "callback",
+            "parameters": [
+              {
+                "name": "popupView",
+                "type": "object",
+                "additionalProperties": { "type": "any" }
+              }
+            ]
+          }
+        ]
       }
     ],
     "events": [
       {
         "name": "onClicked",
         "type": "function",
         "description": "Fired when a browser action icon is clicked.  This event will not fire if the browser action has a popup.",
         "parameters": [
           {
             "name": "tab",
             "$ref": "tabs.Tab"
           }
         ]
       }
     ]
   }
 ]