Allow extensions to pin tabs:...

chrome/common/extensions/api/extension_api.json

 [
   {
     "namespace": "extension",
     "types": [
       {
         "id": "Port",
         "type": "object",
         "description": "An object which allows two way communication with other pages.",
         "properties": {
           "name": {"type": "string"},
@@ skipping 319 matching lines @@
     "namespace": "tabs",
     "types": [
       {
         "id": "Tab",
         "type": "object",
         "properties": {
           "id": {"type": "integer", "minimum": 0, "description": "The ID of the tab. Tab IDs are unique within a browser session."},
           "index": {"type": "integer", "minimum": 0, "description": "The zero-based index of the tab within its window."},
           "windowId": {"type": "integer", "minimum": 0, "description": "The ID of the window the tab is contained within."},
           "selected": {"type": "boolean", "description": "Whether the tab is selected."},
+          "pinned": {"type": "boolean", "description": "Whether the tab is pinned."},
           "url": {"type": "string", "description": "The URL the tab is displaying."},
           "title": {"type": "string", "optional": true, "description": "The title of the tab. This may not be available if the tab is loading."},
           "favIconUrl": {"type": "string", "optional": true, "description": "The URL of the tab's favicon. This may not be available if the tab is loading."},
           "status": {"type": "string", "optional": true, "description": "Either <em>loading</em> or <em>complete</em>."}
         }
       }
     ],
     "functions": [
       {
         "name": "get",
@@ skipping 103 matching lines @@
               },
               "url": {
                 "type": "string",
                 "optional": true,
                 "description": "The URL to navigate the tab to initially. Fully-qualified URLs must include a scheme (i.e. 'http://www.google.com', not 'www.google.com'). Relative URLs will be relative to the current page within the extension. Defaults to the New Tab Page."
               },
               "selected": {
                 "type": "boolean",
                 "optional": true,
                 "description": "Whether the tab should become the selected tab in the window. Defaults to <var>true</var>"
+              },
+              "pinned": {
+                "type": "boolean",
+                "optional": true,
+                "description": "Whether the tab should become pinned."
               }
             }
           },
           {
             "type": "function",
             "name": "callback",
             "optional": true,
             "parameters": [
               {
                 "name": "tab",
                 "$ref": "Tab",
                 "description": "Details about the created tab. Will contain the ID of the new tab."
               }
             ]
           }
         ]
       },
       {
         "name": "update",
         "type": "function",
         "description": "Modify the properties of a tab. Properties that are not specified in <var>updateProperties</var> are not modified.",
         "parameters": [
           {"type": "integer", "name": "tabId", "minimum": 0},
           {
             "type": "object",
             "name": "updateProperties",
             "properties": {
               "url": {"type": "string", "optional": true},
-              "selected": {"type": "boolean", "optional": true}
+              "selected": {"type": "boolean", "optional": true},
+              "pinned": {"type": "boolean", "optional": true}
             }
           },
           {
             "type": "function",
             "name": "callback",
             "optional": true,
             "parameters": [
               {
                 "name": "tab",
                 "$ref": "Tab",
@@ skipping 774 matching lines @@
         "type": "function",
         "description": "Logs a message during internal unit testing.",
         "parameters": [
           {"type": "string", "name": "message"}
         ]
       }
     ],
     "events": []
   }
 ]