Start implementing an auth flow for platform apps to be able to do auth

chrome/common/extensions/api/experimental.identity.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": "experimental.identity",
     "nodoc": true,
     "types": [],
     "events": [],
     "functions": [
       {
         "name": "getAuthToken",
         "type": "function",
         "description": "Gets an OAuth2 access token as specified by the manifest.",
         "parameters": [
           {
             "name": "callback",
             "type": "function",
             "parameters": [
                {
                 "name": "token",
                 "type": "string",
                 "description": "OAuth2 access token as specified by the manifest."
               }
             ]
           }
         ]
+      },
+      {
+        "name": "launchWebAuthFlow",
+        "type": "function",
+        "description": "Starts an auth flow at the specified URL.",
+        "parameters": [
+          {
+            "name": "launchInfo",
+            "type": "object",
+            "properties": {
+              "url": {
+                "type": "string",
+                "description": "The URL that initiates the auth flow"
+              }
+            }
+          },
+          {
+            "name": "callback",
+            "type": "function",
+            "parameters": [
+              {
+                "name": "reponseUrl",
+                "type": "string",
+                "description": "The URL redirected back to your application"
+              }
+            ]
+          }
+        ]
       }
     ]
   }
 ]